Those plastic containers are great. Sometimes the top will nest in the bottom. I’ll poke holes in the bottom of the top (hope that’s not too confusing LOL) and put a couple pieces of tiny gravel in the bottom of the bottom. I nest them and put water in the bottom. The gravel will keep them from nesting too snugly and the water will keep the stuff in the top damp. I’ll then fill the top with seed starting mix. I use this type of thing to start my stevia. I need 2 such identical containers. Because once I’m done spreading the seeds on top of the mix I take the top from the second container set and cover the first set as a humidity dome. WAY cheaper (as in free) than the bought seed starting trays. Hubby snarfs these from the meeting room/snack room where he works before they go in the garbage. All I do is rinse them.
From your description, I know exactly what you are doing. You are a smart cookie. I ordered Stevia seed but that reminds me they are not here, yet. I need to check and see who I ordered those from and when I ordered them.