pile, be piled up, fold up
叠 centers on layering or stacking things on top of each other: piling up, folding, or accumulating in a heap. The idea of folding up fits as a way of creating layers.
叠 is the simplified form of 疊. The older form 疊 likely depicts layers piled up, with 畾 (repeated fields or boundaries) over 冝 (a table or base), suggesting stacking. The modern simplification replaces the top with 叒, which visually suggests repeated elements.
The top 叒 looks like three stacked hands (又 repeated), and the bottom 冝 resembles a table. Picture hands piling things onto a table, creating a growing stack.
For ジョウ, imagine a pile of folded clothes growing so tall it reaches the ceiling: the pile is a 'joe' (ジョウ) of laundry, towering up.