When it comes to a game of pool, there is nothing more important than a smooth playing surface. Aside from leveling the table properly, you can ensure a perfectly flat surface by seaming the slate correctly. On a pool table, there are usually three pieces of slate, giving you two joints to seal. After you have your table set in its permanent place, make sure it's level. Then you can begin seaming the slate.
Heat up the joint using a propane hand torch. Wax seals better when the surface is at least room temperature.
Hold the wax next to the seam and melt it with the propane torch. Melt it into the joint as well as about 1 or 2 inches on each side of the seam.
Scrape off the excess wax using your putty knife. Allow the wax to start cooling, but don't let it harden completely; waiting about 30 seconds works well.
Run your fingers over the seam to ensure that it's smooth with no bumps. If you find any raised areas, scrape off a little more wax with the putty knife. If you find divots or low areas, melt a little more wax into the area and scrape off the excess again.