What you will need: fabric (yeah, I know, you didn't see that one coming, eh?!), velcro (whichever kind works best for you, I only have the sew-on kind), stuffing.
If you have any problems with this wee tutorial, don't hesitate to email me; I'll be happy to help!
You can skip this, but it definitely looks nicer if you iron the mat now, so the edges are flat. Then sew on (or iron, or whatever your kind calls for) a piece of one half of the velcro, about 5 cm (2 inches) from the edge.
Now cut out two circles, or a square or whatever you like, for the pincushion. Sew the other half of the velcro to one of the circles, then sew them together with right sides facing each other. Again, leaving a gap so you can turn it inside out.
Before turning it, though, make triangular snips all the way round the seam, but don't cut into the seam. This will make the pincushion go nice and round. I think doing this has a proper name, but I can't remember what it is, so I just call it triangular snipping.
However, if you're making a square or rectangular shape, you have to snip the corners like you did with the mat before...
Ok, done snipping? Then turn that baby inside out and stuff it to your heart's content. Then sew it together and you're pretty much done!
You might want to do a few seams across the mat, just so the two pieces don't slide about, but you don't have to do this.