Pacing - How do I get myself to slow down?

Here is a trick I do and its helped me tremendously in Quant to keep pace.

"15 min block" recommendation was useless to me. In 15 min, I could finish 7-10 depending on difficulty and that could be nearly 1/3 of the exam.

Before taking a practice exam, I just write this on the side of my "working paper"

Qtn - Quant - Verbal
5 - 65 - 66
10 - 55 - 57
15 - 45 - 48
20 - 35 - 39
25 - 25 - 30
30 - 15 - 21
35 - 5 - 12
40 - 0 - 3

This way, because the clock on the GMAT is a countdown clock, you don't have to reverse calculate. Plus the smaller 10 minute blocks allow me to better gauge how slow or fast I'm going. If I accumulate too much time, I give myself more allowance for the more difficult qtns (esp data sufficiency). If I think I've spent too long on a qtn (which internally usually kicks in on the 2:30-3minute mark), I give myself 20-30s and guess and move on (less if I'm absolutely stumped, don't run through the same logic you've been pondering for the past 2 minutes).

Towards the end, if I feel I've built up a big enough buffer, I give myself the luxury of checking my answer on dubious qtns.

For Verbal, I do the same except I budget 9 minutes per 5 qtn instead of 10 minutes as in Quant. Verbal is harder to stick to as RC tends to take longer, and some SC can mesmerize you, but again, nothing more than 1:30-2min for a SC qtn, and no more than 3-3:30 per RC (this only if you're ahead of the clock)

This has helped me so much especially with Quant to manage my time.