The Easy Stuff:Sewing the springs on to the chair webbing. This was, by far, the easiest part of the whole ordeal. You need to make sure your springs are 'right side up' and are facing the same way. If you know how to use a (big, fat, long) needle, you'll be fine. You need to attach each spring in 3 places, with three stitches at each location. Here's a great Instructable to work from.
Once you're done tying the springs, you cover the whole lot with a piece of burlap. Stretch it over the springs, but don't make it as taut as you would fabric - it needs a bit of give to move with the springs. Staple around the edge and then trim to a couple of inches, fold over and staple again. You'll notice I forgot this step on the burlap on the chair back.
Applying the edge roll and the batting is also easy. It's good too, because after the wine (see below) you need a nice easy step.
Don't ...Don't stagger your springs. I shouldn't have done that, but I didn't have an eighth spring, so I improvised. Do what I say, not what I do?
Don't underestimate how much tying string you need. Get lots. Actually get a roll.
Don't forget to fold over and double-staple your burlap when covering the springs.
Don't forget to pick up a bottle of wine. You'll want it later.
For next time...I still need to master actual knot tying on the springs. I don't have that down. I found online tutorials in this area a bit slim, but there's a guide in Amanda Brown's book "Spruce: A Step By Step Guide to Upholstery and Design" (the best, up-to-date book I've seen!).
Get a long nosed staple gun. It makes all the difference in getting in tight spots, especially at the back of the chair, under the back frame.
Remember to create a 'crown' with the shape of your springs. If you're tying them right, apparently this happens somewhat automatically....I think that's lies. Lies! You'll need to push the springs closer to the chair frame down lower and tie the string firmly. You want a nice 'mounded' chair!
So, when you're done with the tying, you'll want the wine. And probably a good stretch. Or maybe a massage...or all three. You know, whatever.
After the burlap, I also used a deck padding material over the springs - it's a modern product, so if you don't have that just use more (and more) padding. The role of the deck padding is to help cushion the springs so you don't feel them through the foam.
Once you've got the burlap and decking down, attach the edge roll around the seat of the chair. The edge roll softens the hard edge of the frame and prevents your padding and fabric from rubbing against the edge and possibly, over time, wearing out the fabric at this point.
I made my own edge rolling using old cotton batting salvaged from another chair, and some burlap. This way I can create edge roll in any diameter or size I want - fatter for the front of the chair, and smaller for the sides (which get less wear, obviously). Edge roll is a bit like piping or welting on steroids...more plump, but with the same 'tail' or band. I sew mine on the machine - you can also just hand tack it and then staple it down well. This guy makes his own edge roll too and shows you how! His is fancy...you can just use the cotton batting, or thick fabric, or horsehair...whatever. You just need something to soften the edge (but, his is awesome, so for quality, follow his lead!).
This lady with a posh accent will show you how to apply the edge roll. Cheers! (Where she uses shears, you may just wish to use a utility knife, or straight knife). The posh lady forgot to tell you to pinch the front of the edge roll and staple it down, so this guy shows you how. Got it?
Once you've attached the edge roll, you'll see there's a dip between the decking and the edge roll. You'll need to fill that in with batting or padding of some sort - I used salvaged cotton. At this step, you can stack up some padding to improve the shape of your seat's crown. Use this step to fill in any low points or dips created by the springs.
Good work so far! It's starting to look like furniture!