There is a very simple way to stabilize the flange bolts. You simple put a nut on them to hold them upright and steady. There is plenty of space under the toilet for them. I'm sure that setting a toilet quickly and effortlessly is one of the times that practice makes perfect. We DIYers sometimes struggle to do tasks that the experiences pros can do with one hand in their sleep, but that's one of the prices of living in DIY land.