24 cm x 10cm
Put fabric right side together (length-wise) and sew the bottom and length closed. Leave the top end open. Clip corners and turn the tube around to its nice side.
Iron it, making sure the corners are really square (use a pencil tip). Put the top end fabric inside, iron.
Topstitch all the way around, including the open end, to seal it closed.
I used different colour thread for some of mine...variety is the spice of life!
Make a button hole at one end, and sew a button at the other. Job done!
Vintage and quirky buttons make it look even nicer I think, so I used plenty.