Yep they are pretty easy if you have access to an overlocker Bamboo is a tad hard to get hold of right ATM but I've heard it should be on the way. I made mine with a bamboo micro terry outer for the snappi to grip onto and bamboo fleece on the inner with another strip of bamboo terry in the middle.

A 30cm square is a pretty good size to do. That way you can keep using them as a pocket stuffer or booster later on. You may need to fold the front flap over for the first couple of weeks if bub is tiny