I don't have a link to a guide but I'll share my own experience.
I bought a 1 gallon paint can w/ lid from Hoem Depot.
I also bought two 3/8 barbs.
I also bought some "goop" get what you want as long as it water proofs and seals/bonds good.
I also bought a 1/2 inch piece of pipe to use as a fill spout, it didnt turn out so well so we'll forget about that part
Now all you have to do is, buy the appropriate fittings for what you use (either 3/8 or 1/2). Take a drill either the size you need, or closest to the size you need. Drill two holes in the lid of the paint can, then feed your barbs through.. it might be a good idea to have the holes a tad smaller, and use some force when you screw the barbs through.
Next clean it up a bit, rise away any particles, etc. Blow dry it and let it sit and dry. Now apply your good around the edges of the barbs, where they meet the lid, so you get a good seal. You want to do this on both sides - and each time do a water test to see if you need to apply more goop in certain spots.
Your reservoir is pretty much done in now. All you have to do is decide how to hook your pump up to your out let barb. I chose to goop a piece of tubing to the outlet barb, and also goop that tubing to the pump outlet. to feed the power cord I snipped the end and took a flathead screwdriver and hammer, puncturing the lid with the tip of the screw driver. I fed the snipped power cord through, and then re-applied a new plug.
this took me a period of a few days to complete, and I have had no leaks since. You don't have to goop the lid to the can either - as paint cans are good at sealing, plus I simply put duct tape over the top to keep any leaks from doing serious damage. I've turned it all around and upside down and never had a problem yet. My pump has been running 24/7 for about a week and a half now without any problems too.
This is a relatively CHEAP way to make a reservoir, and I designed it as such, seeing as if my pump ever fails I cannot simply replace it, when its all glued together.
I hope this helps, or at least gives you some idea of what to do