Take your piece of foam rubber, fold it almost in half and sew along the edges. Trim untill you get a vague envelope shape. The picture is pretty self explanatory :)
Then open your clutch and stick some velcro on. Be sure to stick both sides of velcro together, stick one side to the upper part of the clutch, then close the clutch so the pieces of velcro are aligned.
Embellish! I used gold thread for the red one and beads for the black and yellow ones.
Aaaand you're done :)