I never tighten bolts on anything till I have them all started.
The 4 holes are asymmetrical so there's only one way all 4 holes will line up. It's possible to have 3 go in and the 4th won't. I put a paint mark on the flex plate and convertor before I install.
Make sure to use blue LockTite on the bolts, convertor bolts are famous for backing out.