Cut your thin plywood pieces to 3.25"x3.25". This is slightly smaller than the 4x4 Scrabble squares. Sand the plywood lightly so edges are smooth. I wanted a finished look so I used my ink pad and dabbed each side until well coated. Let dry.
Next turn the cork over and peel off the backing so the plywood square will stick to the cork. Using an Exacto knife cut cork to fit square.
I then went through the Scrabble dictionary and found the four letter words. I made the words work both left to right and top to bottom. Clever, huh! A little time consuming. Random letters will work for those that don't care.
I made a small dipping spot of the gel glue and dipped the first row just on the right side for the first three letters to stick them together. The next row I did the top side and right side and so forth until you make a little mat. Don't let it sit too long as it may adhere to your paper. Spread a thin layer of the gel glue on the plywood square - not the cork side - and carefully slide the letters on to the top. The gel glue gives you some time to get the shape right. Finally, finish off the top of the coasters with several - I did 8 so it was very smooth - coats of varnish.
I will give 10 points to the first person to tell me which word is not a real word. There is only one.