I used 4x4 wood and my husband cut slices off of it 1" thick. Sanded each piece with an orbital sander, washed each piece with a damp rag then placed letters and numbers (all of the values are the actual scrabble values). I cut out of Silhouette black vinyl on and then modge podged over the letters to ensure they would stay sticking over time then used clear spray paint to seal and give the pieces a nice shine and amplify the rings on the wood.
Each block of wood was attached to the others with flat metal brackets like this one below, we picked them up at a local hardware store.
Inspired by other scrabble wall art like this or this