What follows is what I came up with. It's not Perfect, but it's pretty good, and you'll enjoy having one if you decide to make it.
Best of all though, if you plow through these instructions, I try to pass on the confidence and basic know-how to design and make your own.
CHEAP (almost free), durable, lightweight, roomy, very dry, good star visibility, versatile, sets up easily, DIY pride and skills-building. It's one-of-a-kind I guess, uses very few new materials, and like all great human endeavors, materially registers my existence on earth.
DURABLE: It's overbuilt and performing like a champ so far in downpours, snow, high coastal and mountaintop winds, crappy terrain, etc.
LIGHTWEIGHT: the post office weighed it for me in the bag and it came out to something like 4 lbs--not bad for a 2-4 person tent!
I'd like a tent that blends in with the natural surroundings better, but I had no choice in this because the source tents were yellow and blue.
A con for some people might also be that my design uses guy lines and pegs, which you and your significant other will get into arguments over trying to set up, and then your drunk or stoned friends will trip over in the dark. For me though, these elements enrich the overall camping experience and were 'must haves'.
Step 1: Planning, Materials
First, decide what you want in a tent, and what you'll use it for. Make a list of the features you'd like to have, and all the things that were frustrating or inadequate about tents you've owned and used in the past. Rank these in order of importance.
I wanted: a lightweight, 2-3 person backpacking tent, roomy enough for canoe-camping, with decent visibility through all sides, a mosquito-free view of the stars at night, a fly that came out at least 1-2 feet from the tent walls, and something that would be comfortable to hang around in on rest days, in the rain, without getting wet.
I hated: getting wet in every single tent I've ever used regardless of what it cost, not in the least because of crummy flys that allow the water to run onto or under the tent; poor visibility, crouching around in a too-low tent, clambering over people to pee at night, not having enough ventilation, and having the tie-down points and corners rip out in rougher conditions.
Look at tents on the market and see if any approximate what you'd like. "Borrow" from extant designs, and draw up some of your own. Buy a tent you like, copy down all its dimensions then return it, or just make some pictures using whatever doodling skills you possess. Don't get out the graph paper and start going to town--these don't have to be exact at all.
'III. Seek the Treasure: MATERIALS!
Garage sales and craigslist.org are old tent gold mines.
Families who camped together in their salad years scatter, divorce, get fat, blow out their knees, and buy RVs, leaving enormous tents to rot in someone's garage...and that's where you come in, like a crayfish to a discarded toaster.
I recommend holding out for a giant cabin tent, which will have more solid panels than a dome tent and be easier to make new parts from. When the monied clean house these come cheap, so wait for a deal. (I recently bought an enormous multifamily cabin tent with separate rooms porch jacuzzi tiki bar etc. for a mere 45 bucks. It has more than enough material for the tiny solo tent I want to make, plus next year's christmas gifts for at least a couple of lucky people.....and you can use the scraps to make compression sacks for sleeping bags and clothes, your tent bags, kites, whatever you think of.)
What you come up with will determine what you'll be able to make, so the design phase should really be folded into the materials-gathering phase. If you have an old dome tent or just its poles, you'll be able to make something different than what I made.
As with any DIY project, the genius of your design will emerge from the tensions between available materials, your design ambitions, and your skills set--all of which will be improved in the process: Innovation through Impoverishment + Improvisation.
My Pretty Great Tent is made from a crappy old cabin tent (blue and yellow) someone left the basement of my apartment house that got wet, mildewed, and had its colors bleed--hence the muddy-to-tie-dyed appearance of the top piece in the photos. I also used pieces from a worthy old 2-person (brown) tent a friend gave me after its corner tore out.
III.' Materials Preparation'
Washing: Whether you should wash the source tent(s) first obviously depends on their condition, and/or how much time and $ you want to spend. There are tent-washing detergents out there that might be worth the money. There are probably vegan baking soda and what-all concoctions safe for toddlers and fish that folks have made too; you'd have to check (and let me know b/c a homemade recipe would be great.)
I used a lot of regular detergent and a laundromat washer on the cabin tent for this project. It came out nice, but the waterproofing washed out. Re-waterproofing the cloth when I was done with the tent sucked!, so you should probably only do this if your source tent was as moldy and cat-box-smelling as mine was. (I used a 10:1 solution of mineral spirits and 100%silicone whipped up with the home egg beater to re-waterproof it, but we'll get to that later.)
Dyeing: I wanted to re-dye the material a more natural color: it didn't work on my test pieces, so I guess nylon resists bleaching and dyeing. I suggest seeking materials that are the color you'd like, or being happy with what the Lord provides.
Breaking it Down: Once you're satisfied with the source-tent's smell, begin to rip seams and see what you've got to work with. At this point, just rip enough seams to make the whole thing lie flat, leaving your pieces as large as possible. Don't be afraid to bypass the seam-ripper altogether and just cut through the seams--it saves time and you'll be able to patch together sheets for your Frankentent regardless. Use sharp scissors or better yet a fancy hot-knife which cauterizes your cuts. In the future I plan to modify my soldering iron tip to make it into a cutter for this.
***Be careful with, and SAVE those Zippers***--they're expensive to buy new. Also save all of the loops and webbing and whatnot.