I took the August LSAT and was stressed about getting my writing approved in time for score release. I took it last week and it took less than 24 hours to approve. Not saying this will happen for you, but I was definitely over-stressing. Complete it when you have the time but give your self a week buffer if possible.

I didn't have any real technical issues, but to ease my nervousness I set up a bit over 30 minutes prior and just waited for my window to become available. After that the proctor's in control even if you have some difficulties your test starts when you've gone through the protocol not at the exact time you selected (if that makes sense).