This smiley face piece is the inner gusset, cut out 2.
Leave a FOE tail, you can snip it later, it helps when you need something to pull the elastic through the machine.
I have already sewn the "flaps" right sides to the diaper cut. Here I will sew the inner gussets to the diaper cut.
Excuse the wrinkly fingers! I do a lot of bare handed gardening :)
Here I use a Longer 3-Step Zig Zag so it won't take away the elasticity long term. Increase the length of the stitch.
I really hope this was detailed enough to follow. This is by far my favorite diaper covers in my son's rotation. They are a perfect fit! It is high enough in the front and back to completely cover flats, prefolds, and fitteds. My husband loves that he can use the flats to lay in prefolds so he doesn't have to try and Snappi a wiggly toddler. And best of all, they are mommy made :)