Sorry, no thread or pic yet. I killed all my cameras, and my phone too.
Very simple though, here's the procedure for me, I don't have access to any machining facilities.
Start with stainless washers that are adequate for the nipple diameter.
Shave two third of the thickness on one side, so the top of the washer has an angle when you look at the edge.
Grind the countersink for the nipple head to sit neatly, with a dremel stone or drill bit.
Shape the washer oval so it can be inserted inside the double wall rim.
Smooth the edges to avoid cutting the alu with the spoke tension.
Paint a red dot on the top high side of each washer, so you can see its position when it will be inside the rim.
Start with 5mm alu pop rivets
Cut the rivet slightly longer than the flange thickness
Slide it off the rivet nail
File the tip to the proper length, that would be three quarter of the flange thickness
Drill the countersink to match the spoke head, only deep enough so the rivet can pass the J bend with some fair pressure.
Shape the rivet conic with a file, until it enters the flange hole for most of its length, yet not completely.
Remove the eyelets from the rim if it has some, shaving the top with a dremel until it cuts through, then punch them off.
Use a drill bit the same size as the spoke nipples, to pass it at an angle through each rim hole. Start at the valve hole, drill the two next holes to angle the spokes away from the valve hole, then reverse the angle for the next pair, and so on...
Insert spoke in flange washer
Press the washer to pass the J bend
Drill a hole of the axle size in a stool seat, to sit the motor flat on it
Insert all spokes in the motor flange from the outside
Put a drop of double boiled linseed oil on the thread of each spoke, or your favourite spoke prep
Arrange the spoke crossing pattern before starting to lace, this will avoid having to force some spokes to cross on top of another previously installed
You will need two extra spokes of the same gauge, their length doesn't matter, they will be used as tools
Pass one of the tool spoke through the rim from the inside to the outside, insert through one rim washer, screw in the nipple, then screw the second tool spoke at the nipple head.
Slide the rim washer on the inside spoke and push it inside the double wall of the rim
Push the nipple inside the rim, and play back and forth with inside and outside tool spokes until the nipple finds its way through the rim washer and the nipple hole.
Hold it seated and unscrew the inside tool spoke, then screw the nipple on the wheel spoke a few turns, hold the nipple and unscrew the outside tool spoke.
One is spoke done, repeat with all of them, screw each of them the same number of turns, and be careful to respect the lacing crossing pattern
With a screwdriver, screw opposite nipples alternatively, the same number of turns. until they start to be hard to turn.
Do the matching pair, the same way, keep the turn count.
When they are starting to offer some resistance, don't screw any further.
Screw each nipple the same number of turns that you counted with the first pair.
You have a wheel. It is near true but not tight nor dished.
Measure the dishing that you need to center the rim with the bike frame
With one of the tool spokes, turn each rim washer until the red dot can be seen on the side corresponding to the spoke closing angle
Start binding the spokes, each the same number of turns, on the side that you need to dish to.
When the screwdriver will start to slip off the nipple head because of both the resistance and the angle of the nipple
Screw the nipples of the other side, each the same number of turns alternatively, until the desired dishing is nearly achieved.
Punch each spoke head in the flange washers, hard enough to make the flange washer sit flat on the flange.
Tighten all nipples after making sure the red dot is still on the proper side, both sides the same number of turns of course.
You can install the rim band, tube and tire now, for the rest of the job will be done with a nipple key
Find a place to spin the wheel, it could be on the bike upside down.
Adjust the spoke tension accordingly, until the wheel is very close to true
Lay the wheel flat on the stool again and press each side with all your weight, repeat around the wheel, both sides
Back to truing the wheel again, you can give an extra punch on each spoke head, to sink it a tad further in the flange washer before final truing.
Ride the wheel, cornering hard, braking hard, then true it again
You have a good wheel, you deserved it