You have three fifths enough tools to build a stand for a 20L. The three missing tools are a tape measure or accurate yard stick, a screw driver and a set of band clamps to hold things in place while you glue and screw it together. Conveniently enough most $ stores carry a card of four ratcheting band clamps. The call it a luggage compressor or something like that. If you are careful in drilling and screwing things together you can omit the band clamps.
Your next tool purchase, by the way, should be a $35 - $60 name brand random orbit sander. After you do something with it that would have taken hours by hand, or been torn up by a belt sander, you won't regret the purchase. I have two now and keep 120 grit on one and 220 grit on the other. I have a belt sander but rarely use it since finally trying a random orbit sander.
The stand will be made of straight flat 1x3 or 2x4 stock which you can cut with your miter saw. Been there done that. In college I once built a whole room of furniture and cut all the wall paneling with a hand powered miter saw. (back saw) If you have a miter box so much the better. Also, you may be able to ask the lumber yard or big box store to make your cuts for you. If they charge you for cuts, make sure they cut the pieces accurately.
You will need a tube of wood glue and coarse threaded drywall type screws that are a bit shorter than two times the thickness of your chosen wood. I purchased a decent counter sink to allow me to set the heads under the wood surface. A bit of filler and the screws are out of sight.
Please read and follow the directions on the glue bottle. Glues change but guys generally don't. Reading the directions might save you a lot of time and sanding. For instance - polyurethane glues (Gorilla glue) shouldn't be applied like white or yellow wood glue.
Now search for the stick built stands and get to it.