I built many melamine enclosures during my first 10-15 years of keeping and usually built them on my own. The first two sides are always the most difficult. Once you have connected sides together you should have no trouble. You just need to hold the first pieces in place until you have three screwed together so it can support itself and each new side. I used to have a steel frame I'd lean one piece against on its side, put the second down on top of it then screw down into it. Then I'd lay those two on their side so the third could sit flat on top, screw down through that. I'd then have three sides giving me something stable to build on from there.
Alternatively you can get creative with clamps, tape, awkward use of feet, legs and elbows, etc. If you have a table, bench or other object of around the same height as a piece of melamine you'll be screwing down into you shouldn't have trouble.
You definitely don't need three or four people. I've built some with friends and it definitely does help and makes things faster and fun, but most of mine were done alone between about 10PM and 4AM when I was a uni student.
If all else fails, invite a friend over who has some experience building stuff, or if you don't know anyone suitable, offer a slab of beer for any willing experienced herper who wants to help, and if you don't live in Timbuktu you should soon have a new herp friend.