I don't sleeve my line sets which makes the sets a lot easier to make. Here's an overview of how I do it.
The most important thing, that is overlooked or minimized by a lot of folks, is proper stretching of the raw line.
Sharp knife or very sharp scissors
lighter or matches
I put a 1/4" screw eye (pried open a bit) or hook into a strong fence post or telephone pole which is strategically placed in enough open space to run the length of line I need to make. About waist high. A heavy hook or loop in a solid surface is important. Check the hook for burs or rough spots and smooth as needed.
Mark a spot the distance from the hook a little longer then the lines you need to make.
Run the end of the spool of raw line through the hook and holding the spool in one hand (spool on a spindle, like the sharpie marker I use later) and the end of the line in the other, walk back to the mark.
Cut the line (melt the cut ends with the lighter) and tie loops in each end with two overhand knots close to each other.
Put the marker pen or some other rod through the loops and pull the line tight.
You may notice that after the first pull the line doesn't spring all the way back to its original length. Keep pulling and releasing the line until it seems like it''s stretched as much as it going to. I probably do this at least 10 times.
How hard to pull? As hard as you can without breaking the line. Be gentle and work up to a hard pull each time. You probably couldn't break even 90# this way, but if it did, it would break at the hook or the loops, so it wouldn't be a big deal and your line would be well stretched. I did break cheap 50# once this way. With heavy line, you'll be glad you have a solid hook.
Once the line is stretched, carry the loops down to the hook, swap them for the middle of the line and carry the middle back to the mark.
Pull the line tight with the line around some small diameter object. I use the cap of the sharpie marker.
Here's the key to even lines. Don't do this on a windy day and make sure you have good light to sight down your lines.
Pull the lines tight and if they are evenly centered on the pen cap as you relax tension you will see them droop evenly. That's the key. There should be no wraps in the lines at all for this to work.
Sight down the lines and gradually release tension. Because there is not much friction on the plastic pen cap or whatever other shaft you use to stretch the lines (I've used a screwdriver for heavy line) the lines should be automatically centered around the shaft. Stetch them tight again and with the pen mark the line at exactly the apex on the shaft. You've marked the exact middle point of the line.
Cut on the mark. Melt the ends.
Even up the cut ends and put a mark across both at the same time with the marker at the lenght you wat your loops to be. This mark will be the final length of your lines.
To tie the loops evenly, fold one line over art the mark and pinch it at the mark between your fingers. Spectra holds this crease pretty well. With a little practice you can tie an overhand knot without disturbing the loop. Tie one know in each loop for now. Put the loops over your pen shaft and pull tight. If for some reason the lines are grossly out of whack only one will come up tight. Even if you goofed a bit tying the loops or at some other stage, the lines should be very close.
Use the droop test. The line that droops first is longer, by as little as a 1/16". If something is terribly wrong you can untie the long loop and retie it, but I've never had to do that. the worst set I've ever had this way only required an extra knot or two in the loop to shorten up the long line. So, you'll end up with at least two knots in each loop. And you're done.
As for attaching non sleeved lines to a kite, there are three ways that make them easy to remove without damage from picking at the tight little larks head knots with fingernails.
Tie a little pigtail loop at the end of your main loop that sticks out and gives you something to grab with your fingernails.
Tie loops with heavier line which is easier to untie and larkshead your lines to those, then the hevay loops attach to the kite.
And, my preferred method: Tie a second knot in the bridle pigtail about 3/4" from the end. Fold over the pigtail at the knot and larkshead the unsleeved line to this folded over knot. Pulling the end of the pigtail releases the the flying line .