"Go to your local bike shop and have them add the spokes
not always that easy, in January I went to several bike shops to have a 20" disc wheel built, sorry come back in a few weeks, or sure we can build it, if you already have the spokes cut. This is in Chicago, not some small town that's lucky to have a bike shop. Well, I went on u-tube and saw various 36h bmx builds. I bougt a front disc 36h hub, got 36h rim and after measurement, order spoke cut to right size, watch u-tube as I assemble a wheel. did this about 4 times before I got it correct, now it is second hand, I have built 6 wheels since Jan/2012. these are all either disc or sturmey archer drums.
this is the spoke calculator that I use. http://lenni.info/edd/
Motobecane ..bafang front driver.. 42v
24" girls bike ..ebikekit 20" fwd..75v
24" Schweinn 9c 20"rwd 75v
26" Schweinn Yescomusa 48v 800watt dd
Easy Racer clone LWB.....24" rear e-bikekit 48v ..ready for testing
Hooligan clone , longer rear chain stay.. twin 20"...
fun bike...twin 16" wheels. small rear motor... ready for testing
convert my CLWB recumbent to a front bafung@48v..ongoing