Marty Milkovits replies: Mix up a 10% solution of glycerin and distilled water. Using a spray bottle (empty Windex bottle is ideal) saturate both sides of the veneer. When the veneer becomes pliable, press it between plain paper towels and brown paper (like shopping bags, NO store labels) sandwiched between plate glass. Weight this down at 5 lbs ± for 1/2 hr and then change the paper and repeat. Do this every hour or so for the first day. If you are not going to be using the veneer right then, press it between maple or birch plywood until your ready for it. Check it every day or so and change the plywood if it shows any signs of dampness.
Al Breed replies: To flatten burl, either make a thin sizing solution from hide glue and clamp up the pieces between boards and paper and change the paper until the veneer is dry, or use the flattening solution from Woodcraft and follow the directions. With the hide glue method, you’ll have to clean the paper off the veneer with a sponge and water.