Do one area at a time. Keep going over say just the tail (or one edge or whatever) until your board is warm (not hot) all the way through. The wax will stay liquid for a few seconds rather than freezing immediately. Then move on to another area. You can't just move the iron all over the board frenetically and expect to heat up the base and expand the pores you want to absorb the wax. Just my .02 after waxing 3 boards myself and watching a ton of vids.