I use the Lil K30: https://www.lilpackaging.com/double-wall-cardboard-boxes-strong-cardboard-boxes
There are several folds to reduce the depth.
Altogether I use:
K30 for the largest sets (Firehouse HQ, BWE)
G30 for next tier (CLAAS, High Speed Passenger Train)
CPL45 (Krennics Shuttle, Spiderman Bridge Battle)
G10 (Poes X Wing, Winter sets)
E4 (Telehandler, Ecto-1)
E1 (Eiffel Tower, Carbon freezing chamber)