Here's a tutorial you may enjoy, Julia:
Hi Julia, here's a tutorial on how to build an outdoor storage ottoman https://jenwoodhouse.com/strong-tie-storage-ottoman/
If you can find an old wooden box with a lid upholster it and cover it with weather proof fabric. You could also build your own box with pallets
I found an old ottoman at a garage sale and redid the cushion with a vinyl tablecloth and new foam. I painted the legs with an outdoor paint from DecoArt. It is so comfy and adds some color too. https://michellejdesigns.com/outdoor-footrest-makeover/
I love how this one can serve as an ottoman an outdoor coffee table: https://jenwoodhouse.com/strong-tie-storage-ottoman/
If you are looking for something to just rest your feet on, take the back of a patio chair off, attach a outdoor cushion to the bottom and tie with strings, and you are done....