We saw this idea in a Lowe's freebie idea magazine last year and made one for my dad. He and Miss M LOVE to play tic tac toe, so this was the perfect gift for him. I bought enough supplies for a second game and just now got around to making one for our house as well.
Easy and inexpensive supplies:
slate tile (Mine was $1.97 @Lowe's)
bag of river rocks (Some Dollar Tree locations in my area carry these.)
4 felt sticky pads (Dollar Tree again, but they are cheap at other locations too.)
white paint (on hand)
polyurethane (on hand)
Draw out your tic tac toe board on the slate. I sketched my lines in white chalk first because I knew I couldn't free hand it very straight! Paint the lines with white paint and seal with a coat or two of polyurethane when dry. Miss M helped me paint the X's and O's on the rocks - 5 of each. Attach a few felt sticky pads on the bottom and you are all set. This is a great little game to have out on the coffee table or outside on the porch!