Just like cooking it, lots of ways to do what your asking.
As for me, I'd not slice it, larger meat retains more moisture. Vacuum Seal, freeze it. Thaw it out and warm in your own pit if you don't have access to Alto-Shaam or other oven.
Slice like its fresh off the pit. Just did 18 like this and the only ones that came out dry were cooker ( me ) error before they were frozen.
Best of Luck!