Overalls with short legs. Button bands in the crotch makes it easy to change the diaper. Fitted waist and comfy, loose fitting around the bottom makes this easy to move in.

Knitted bottom-up. You knit the legs flat separately before joining them in the round with new stitches between each leg. Work short rows in the back and decrease on some rounds before reaching the waist.
Work a rib and cast off most stitches. Knit straps with the left over stitches.