The grain in veneer is particularly important as to its effect on the figure of wood. Different types of irregular (highly figured) woods may raise, crack or blister. Some of the best examples of this are the burls and crotch veneers.

The first prerequisite for a good veneering job is that the veneer must be flat, clean and dry. Because of the modern method in which veneer is manufactured and the nature of some highly figured woods having no grain direction, they are most often supplied wavy or buckled. The following procedure should be used to flatten wavy veneer prior to bonding it to a surface.  It's important to note that this procedure should only be performed on raw veneer (without any backing).  Flexible or paper backed veneer will be damaged if you try to flatten it using the technique described next.

Materials:
Glycerin - is a common wetting agent that slows down the drying time of many solutions.  It can be purchased at pharmacies or online from woodworking supply companies.
A Spray Bottle - same type you would use to spray garden plants
Brown Craft Paper - Can be purchased at stationery supply stores, art supply stores or home centers

The Procedure
Prepare a solution of 10 percent glycerin to 90 percent water. Pour this solution into a clean spray bottle (the type used to spray plants). Set the spray nozzle to spray a very fine mist.

Using the mist bottle with the solution you prepared in the previous step, mist both sides of the veneer. Place the dampened veneer between two sheets of brown craft paper, (make sure there is no print on the paper).

Next, place the veneer and paper between two panels. Any stable, flat panel material like MDF, particleboard or plywood will do. Add a minimum amount of weight to the top and leave overnight. Examine the next day, if the veneer is still not flat, repeat the process using new craft paper, this time the veneer should be flat enough so you can clamp it between the panels. Once again leave overnight.

Once the veneer is flat, do not apply any more solution, but change the craft paper every day for about 5 days allowing the dry craft paper to absorb the moisture that you have added during the flattening process. Keep the veneer clamped between the panels at all times until you are ready to bond it. Make sure you have everything ready to go (glue, clamps, roller etc.) before you remove the veneer from the clamped panels.