Neo Angle Shower Base Leveling

Hello everyone. I've got a question that hopefully someone can answer for me. I'm installing a neo angle shower in my new bathroom. My subfloor was unlevel, so I built some forms and poured some self leveling cement to level the shower area. After the first pour, it was still a little out of level so I did a second pour. The area is now level; however, when I place my shower base on it, it still rocks a little which I'm concerned about. Especially around the drain area. The only thing I can assume now is that the shower base itself isn't completely true. What I've been thinking is perhaps I can lay some kind of a mortar bed, connect my drain assembly and just set the base in place level and let the bed dry. My question is would this be okay and are there any suggestions for a product to use for this. I was thinking a thinset mortar but I'd be glad to hear if someone else has another suggestion.

Thanks in advance for your advice everyone.

SLC requires lath on a wood subfloor and primer. Did you use those?

What often is used is something like Structolite or deck mud. Deck mud is a sandy mix of 4/1 sand to portland cement...the same stuff as used in making a traditional shower pan. The mix can be from 3-5 parts sand. You'd throw some down then mush it into the mix, leveling it carefully then leave it alone for awhile until things set up.