Wooden crates can be used to make all sorts of furniture cheaply and often more sturdy that the build your own laminated particle board they sell in a lot of stores.
The best places to get crates are craft stores, always check for coupons and deals first.
First you will want to sand down any rough edges on the crates, then apply stain in one or more coats to get the color you desire. I am using a Sedona red applied twice. It’s the same stain I refinished my plant stands with. There is a slight difference due to the type of wood differing but it is very close. Apply a sealant or lacquer after the stain has dried to protect the wood.
When it is done and completely dried use short screws or nails to affix the crates together. I used one of the simplest designs for this because I needed it to stay in it’s small space.
I plan on a small square coffee table as well but I went with the TV stand first, I will eventually do both but it is the rainy season now so probably in the spring, that way I have two matching pieces of furniture. Here is the standard arrangement for making a coffee table.