Hey girls,
After many-many years of making IB covers, it is a easy thing. Buy heavy cotton interlock and cut it about 3 or 4 inches bigger than the board (just lay it on top. Have the stretch going the length of the board. But 1/4" or 1/2" cotton elastic and zig-zag it aroung the edge of the fabric stretching as you sew and stretch pretty taunt around the front and back and then turn it under and go around it again. Makes a good cover and if it needs to be tighter, get some of the metal clamps that fit underneath from side to side. Washable and even can be cloroxed if needed.
Peg=TX