Step 1: Parts & Tools
Enough 1/4" plywood to complete the project, higher ply number the better
Wax transfer paper, available from any office supply or craft store. AKA t-shirt transfer paper
Text editor with options to mirror the output print.
Iron, some heavy cotton
Narrow gauge circular saw or band saw
Overview: A mirror image it printed on to the transfer paper, ironed on to the wood and in this case cut up in to individual tiles.
Step 2: Layout print
I've attached an example html file which you should be able to enlarge to fit your paper (A4 or US letter) using the (CTRL) key and '+'. Alternatively import this in to word to manipulate.
Some things to note.
The letter in each row and column should be centered both horizontally and vertically within each cell, which is why I chose html over word.doc.
Leave enough room between each letter for the width of the saw blade and a little. You will also want to chamfer (round off) the edges of each tile
Start with a trial run, print the image on to plain paper and place on the receiving surface to make sure everything is laid out correctly. When you're happy, print to the wax paper.