I'm making a custom monster, a huge flesh golem. I'm trying to determine its unarmed strike as a much larger monster for slam, and need to calculate its damage to determine its offensive challenge rating so I can calculate its actual challenge rating.
So far I know that the medium sized Flesh Golem has these stats for slam:
Slam. Melee Weapon Attack: +7 hit, reach 5ft., one target. Hit: 13 (2d8+4) bludgeoning damage. (MM p.169)
I get that hit dice use constitution to calculate hit points, but when I tried to apply the same equation with strength to determine damage I was off, which makes me believe there is a formula I just don't know.