“I have a question: What can you coat wood with so it is not toxic, but it prevents water and soil from rotting the wood?”
Here’s a bunch of choices, but the most economical is Linseed Oil.
https://redemptionpermaculture.com/how-to-safely-treat-wood-used-for-raised-garden-beds/
Starting your plants with Seed snails. (14 Minutes)
Something else on Growing potatoes in Boxes. Probably best for determinate potatoes! (17 Minutes) What happens when you plant your potates in cardboard boxes James Pirgioni 4