Here we go! This is what you'll need. Mod Podge, Elmer's washable glue, and a piece of cardstock.
Step 1: Brush the Elmer's glue onto the cardstock in a nice smooth layer.
Make sure you cover the area where you will be printing. Let it dry.
Step 2: With an inkjet printer, print an image onto the glue side of the cardstock.
Step 3: Brush a smooth, thin layer of Mod Podge onto the wood.
Step 4: Stick your image face down onto the wet Mod Podge. Press and smooth to make sure the image has good contact with the wood. Let it dry OVERNIGHT. Don't peek too soon!
Step 5: Soak it. You can dunk it in water, run it under a faucet, or squirt it with a spray bottle. Let the cardstock get really wet and soft. Gently peel off the cardstock. I held this under running water while I peeled it. You can gently rub the image with your finger tip to loosen any remaining paper pulp.
Step 6: Voila! And no plasticky decal edges! The Elmers washes away completely. Totally smooth!