I'm building a small two-pedal board because I hate pedals moving around during a gig, and a big pedalboard is an overkill for one band I play in. I want to cover a 6"x10" piece of wood which some material so that velcro will stick. What "easy-to-find" material should I use? Haven't found anything yet except carpetting that is too thick, or material that is not easy to glue to wood.

Just use that velcro that comes with both sides and put the fabric part right where you want the pedal to be.

Or any kind of fuzzy material will do the trick.