If you want more depth, I Can Sew This features a "bitsy" box pouch tutorial. Visual Inspiration

iThinksew has a fun pyramid-shaped pattern that stands out and is great for holding small trinkets.

Crazy Little Projects offers a simple rectangular pattern perfect for cash and cards.

Two 5" x 4" pieces for the exterior and two for the lining. Zipper: One 4" or 5" nylon zipper.