I'm building a mortar bed shower with a CPE shower pan liner. One of the wall will be built with 8" x 8" glass blocks. I was going to place the pan liner over the curb then float the 2x6's with mortar. I need advise on how to set the first row of blocks. I was thinking of using 3 2x6's stacked as a base. I'm concerned about the inside of the block wall where it meets the base and if it will seal properly. Please help with any advise.