We used a shallow wooden box turned upside down until someone decided they needed it more than I.
So I now use two of these from Harbor Freight. Zip tied two together and it works (about the same size of the steps). Not the best but better than others so far. It does not sink into mud as much, about the right height and will fold up (priced at $7 each). Wood blocks are no bueno, they flip over easy and attract mud. Steps with round legs submerge into soft sand and mud.
https://www.harborfreight.com/one-step-folding-stool-black-57576.html?_br_psugg_q=step+stool