I undress myself, put an unfolded and fluffed-up diaper on the floor, sit down onto the diaper, lay down onto my back, make sure that the front and back of the diaper are at equal height, then I first tape the bottom two tapes, then the top two tapes.
In the past I put the bottom tapes around my thighs, but I switched to putting them halfway the front of the diaper. I think that this leads to less leaks. The top tapes should go near the top of the front of the diaper!
When placing each second tape (of the bottom and top), I lift my bum and pull both sides together, so there’s a little tightness. If you’ve diapered yourself a few times, you’ll know where to play the first tape, to make sure that the diaper is perfectly centered on you ^^ !!