Use the noun welter to describe an enormous, messy pile, like the jumble of papers, coffee mugs, pens, and food wrappers on the desk of the messiest person in the office.
Welter can also be a verb — the items in the pile on the messy desk welter every time someone tries to pull something out. This means they roll and get tossed around. Maybe the person isn't as messy as you think. Possibly his projects keep him so weltered — meaning "deeply involved" — that he doesn't have the time or energy to deal with the mess.