After printing and cutting out the sewing patterns you need to decide on one of the wing variants. The first variant is the simplest, it's rounded and looks cute. The middle variant has a little detail and the third one is for people who like to make the wings more realistic. In that case you should transfer the feather details to the outer piece of the fabric and embroider them.
The belly also comes in two variants, one is round and the other has an edge.

First of the fabric should be ironed, that makes everything easier. When tranferring the pattern take care to make two wings in reverse. The body and the belly are put on folded fabric so that the edge of the pattern sits exactly on the edge of the fold. (Alternatively, you transfer the first half to the fabric, mark the edge and fold the pattern over to draw the other half.)

Transfer all parts with a pencil or trick marker to the left side of the fabric. When cutting out leave an additional 1cm seam allowance on the body and wings. If you make belly, beak and eyes from felt you don't need a seam allowance on those. If you want to make the belly from fabric though you will need a seam allowance on that part too. Transfer the missing body and belly halves to the other half of the folded fabric.
I cut out the dotted parts on the body pattern too and thus transfer the positions of the eyes and belly to one piece of body fabric too.

By sticking fixing pins through the marked positions on the left side of the fabric I can locate the right place for the outer eye ring on the right side. (Since the fabric has a regular pattern two pins are enough in this case - on a busier fabric I'd recommend using four or more.) Place the felt within the markings, fixate it with a fixing pin and remove the other pins again.

Sew the outer eye ring by hand with a regular stitch. If you like things extra tidy you can use your sewing machine for this.

Then do the same for the belly. If your belly is made from fabric I recommend to make cuts into the seam allowance all around, then bend and iron it to the back. That way it's much easier to sew on.

The eyes are also sewn on by hand. By changing the position of the pupils you can achieve a wide range of emotions. Let Owlie look upwards, sidewards or make it cross-eyed. You could cut half circles from felt as eye lids and make her sleepy, too.

As a last step, sew on the beak.

This is what it should look like when it's done.

Tip: If you prefer your craft items to look a bit more crude you can sew and stuff Owlie first and then attach the appliques with random stitches by hand, of course.

Next up are the wings. Place one wing half and a reverse piece left sides together and sew them with the sewing machine. (Of course you can do it all by hand if you don't have one.) Leave an opening of ~2cm on one side for turning and stuffing.

Make little cuts in the seam allowance all around the rounded edges while taking care not to hurt the seam. This way the wings look smoother after turning. Cut back the seam allowance to 2-3mm all around.

Turn the wing - I use a haemostat for this. If you don't own a turning tool better leave a slightly bigger opening. A thick knitting needle or chopstick can be helpful too. Stuff the wing lightly and close the opening by hand using a ladder stitch.
Repeat for the other wing.

In case you use wing variant 3 the feather detail has to be embroidered before sewing.

Next up the darts in Owlie's body are sewn (the triangle indentation at the bottom). I recommend to fix them into place with pins and then baste them before sewing them. This will become the bottom, so Owlie can stand.
Fold the fabric right sides together for this.

Place both body halves right sides together and fixate them with pins. Since this almost always generates some variation I sew with the side with the face showing upwards. If I would sew along the markings on the back part and both halfes are not placed exactly on top of each other the face might become misaligned.
Baste at least the bottom to make sure it fits well together.

Sew all around with the sewing maching, leaving an opening of 5-6cm at the bottom for turning and stuffing.

Turn Owlie right side out, then stuff it. Use a knitting needle, chopstick or haemostat to stuff the ears first, then work your way up to the bottom. Many stuffing materials tend to shrink a bit over time so stuff generously and tight - but not so tight that the seams burst!

After stuffing close the opening with a ladder stitch.

Tip: If your Owlie is supposed to stand firmly (e.g. as a bookend) sew a small sack and fill it with clean pebbles, sand, rice or heavy pellets and position this sack in the bottom of Owlie's body. It should be wrapped by stuffing so Owlie doesn't get an unsightly bulge and depending on its size you should leave a more generous opening so it actually fits through.

As a last step Owlie gets wings. You can use various methods to attach them. My Owlie uses buttons. You can also use beads, decorative embroidery thread or attach them invisibly by just sewing their underside to the body (which might look more attractive with wing variant 3). Up to your taste!
If you use wings with detail make sure that the smoother edge shows forewards and the wavy edge to the back.

I used an extra long doll needle (13cm) to sew on the wings. That way I could go completely though the body and attach both wings at once. If you do such projects at least now and then it's a useful addition to your tool stash. It's not vital though.

Well, Owlie is done! Have fun with it!