Hunter-Steve, 'tis true. Better to begin during cooler weather but if gotten on quickly and covered entirely in salt without meat touching one another or the side of box meat can be preserved in 90° weather. 2" salt layer on box bottom, pack salt around all sides, 1" salt between layers. Top layer should be covered with minimum 2" salt.
Drill holes in box bottom (for liquid drainage) and cover with a clean fabric before adding salt. Lid can be one piece but i prefer 2, split in middle. Have someway to secure lid or critters will get into it.
May want some sort of catch try for the drainage. Sit box on 4x4’s to keep off ground.