I made some self-cover buttons using some scraps of canvas and a bag of odd bits of tapestry wool. The design is supposed to represent the centre of a flower. I cross stitched a circle roughly the right size to cover the top of the button.
I cut the canvas into a circle shape the right size to cover the button and tuck in under its snap-on back, then I gathered the edge and tucked it in. I had to put the back on slowly and make sure all the edges stayed underneath the back, so it took a little longer than making a button covered with fabric.
I am thinking of using these buttons at the centre of flower brooches.