I had to learn as a kid too and I think I'm pretty good at it. Once in a while a tape will slip into the wrong spot if I'm in a hurry and then I fix it, but I have a pretty good routine down.
I lay down on the corner of my bed with each leg hanging over the side, so the corner of the bed is between my legs and my legs and kinda dangling. Then I slip the diaper under me, I just put my feet on the mattress frame and push up. The trick I found is that I wrap the diaper around my back exactly like I want it to fit and make sure both sides are even on my hips so I know that I'm in the center. Then I pull the front up tight through my legs and up on my belly and check to make sure that the front is the same height as the back or even a tad bit higher since I sleep on my belly and sides.
Once the positioning is good, I hold the front waist band in the center on my belly with my right forearm so pulling on the wings doesn't twist the fit. With my left hand, I pull the left wing tight around my hip from the center of the wing so that its snug (but not too tight) and even (not loose on the waist or leg), exactly how I want it to fit. Then without moving my forearm, I use my right hand with fingers spread out to hold the wing in place and pull the bottom tape into position. I pull up and around to be sure it's snug around my butt cheek and sorta follow the natural angle of the line between my butt cheek and leg up and around to the front and at an upward angle on the front of the diaper. It helps to let my legs dangle here so that when the tape sticks the diaper is nice and flat on the front, not all bunched up.
And here's my little trick. Once I'm in the right spot with the tape my right hand is still in the way holding down the wing. So right before I tape I twist my wrist down so that I'm holding the tape in my fingers with the back wing wrapped taughtly around the front now and the palm of my left hand now holding everything down in place. Then I can slip my right hand out of the way still without moving my forearm, and stick the tape down in the exact spot I want it.
With that tape in place, I move to the right side, never letting go of the front panel (or the tape might pull the front panel over and make the diaper feel twisty. I just slide off my right forearm from holding the front down and switch it with my left. I usually give the front panel a little tug here too just to make sure it's still centered and hasn't pulled to the left after putting the first tape on. Then I repeat all the same steps with the right side leg tape (just reverse the hands).
Once both leg tapes are in place, I can let go of the front panel because it'll stay centered now, and I double check that the back is still as high as I want it as well as the front. Sometimes I wiggle a little and have to adjust, but that's easy, I can just rotate my hips a little and pull the diaper back in place. This helps make sure the diaper is snug in the bottom and avoids what I call the butt pouch look.
Then I just tuck the front waist into the back wing and pull the front tapes around following the natural angle over my hips and tape on the front in a slightly downward angle on the front. Once that's done I can either fold the front waist in if there's a little extra and this helps protect against leaks when sleeping on my belly, or just leave it if I'm gonna put pants or shorts on so that that front sticks out a little over the waist of my pants, which helps keep my clothes dry.
I also learned as a kid to close my eyes during the whole process because I get distracted if I try to watch myself doing it. When I close my eyes I can just feel how the diaper fits and where the natural contours of my legs and waist are. It helps a lot because my fingers just always seems to go into the same spot just from doing it so much and knowing how my body fits.
Doing it this way makes the diaper fit my body exactly which keeps me comfortable and my bed or clothes dry. Sometimes other people have tried to change me, but even though they try to be helpful, they usually do a horrible job because they're inexperienced. Nobody likes wearing a wonky diaper so I just fix it when they're done which is usually kinda funny. At least they tried
