Most people eat eggs, and I know that EVERYONE needs toilet paper (well, except my GF; some surgery involved), so here is how you can combine the two, to create biodegradable starting pots that are not only easy to make, but stack easily for compact storage!
You will need an adhesive that is waterproof to tack them into position. Let it dry and then really lock it in to seal it all together. Some people use hot melt glue, but I don't like it. No telling what is in it, plus, with the wood glue, I can reposition everything if it gets tilted, while it's curing.
To use, all you have to do is take a long knife and slice them apart when ready to plant. Just be sure they are not wet or they will fall apart! DAMP only! Put them directly into the ground and they will compost down.
So here is what you need: Egg cartons and TP tubes or even paper towel tubes. They are both the same diameter. Just make sure the length is the same (2 1/8" to split a TP tube in half). Scissors and glue. Pretty simple.
Here are a bunch all glued up and drying.
Like I said, these are stackable and will take up little space.
One final note: Don't switch brands or they will not fit! Some brands have a tilt to the lower portion and you will need to turn them back and forth to stack straight. Others are flat and don't need any special attention. All in all, this is a simple and cheap way to make biodegradable pots. Peat pots never dissolve (Mary, I am looking in your direction, LOL), so these are a great way to use trash to make treasure.