Start with your Platform(s)
You can use any Variation. I have found that two layers with a three block space works the best. Although for a really long game you could add multiple layers of leaves.
To start, simply replace the planks with leaves
You can do this easily with World Edit, it takes two commands to do this “//replace 5 18” and “//replace 18 18:3” Or you could do it manually by using replacing the wooden block with a leaf block.
An unlucky player already fell to the bottom tier
Two layers allows for a second chance if you are lucky enough to fall onto the second layer after the leaf block underneath you disappears.
It really starts to get hectic once the leaves have deteriorated
This is when the panic really starts to set in and you may be better by picking one block and staying on it.