Martha simply sews four ribbons into a board pattern and suggests using rocks and seashells as x's and o's. Read about it here. It also seems like you could use masking tape in place of ribbon for a non-permanent board. Anna Maria is a sewer (and designer of wonderful fabric) so this project does involve some sewing. She makes towels into backpack-esque totes to avoid the inevitable dragging in the dirt or, worse, the temptation to snap them. If you take your kids to the Y or elsewhere for swimming classes, this totable towel could be useful all year round. Read Anna's instructions here.