I'm installing a 32" x 48" Kohler shower base in a basement with a floor that is not level. It pitches about 1" from front/left to rear/right. It is framed out and I'm wondering what would be the best way to set this base? I'm thinking the best two options would be to just use mortar or to use self leveling to ensure equal support, then mortar to set. Any advice from you experts would be greatly appreciated.