i'm confused. if the dreamself is killed or used to kiss-revive someone, then how would that player get to their sacrificial slab? i mean, i know they'd need to travel to their respective moon, but just how easy is it for a waking player to get there? is it just a simple gate-hop away or what? and then where even is the/an entrance to the core to even get to their slab?

Sacrificial Slabs are typically in the moons of Derse and Prospit. All a player would have to do is fly there.