I'm _told_, though I've never tried, that home BGA is pretty easy with a hot plate or oven, if you're assembling a new part rather than reworking. plop down the part in a layer of flux, with the balls in approximately the right place (like, 40% overlap is still okay), and bake. When it hits reflow the balls and pads self-align and you're done!
Tricky bits are you can't inspect the solder joints, and if you need rework you're a bit fucked (hot air + reball + reinstall, doable but ugh)