Daniel A. Nagy's process to align incentives in remote work: A) agree beforehand on target hourly rate & hours for each (small) task; B) pay target hours*rate, NOT time spent; C) measure actual time to improve future estimates; D) keep renegotiating to address the unexpected.
Agreeing on money matters beforehand also rather than after the fact can save a lot of pain. Both parties will make mistakes, but they should wash out after time. Any irreconcilable disagreement can be resolved early and without bad blood.
Read my blog!