I am not an expert in medical manufacturing, though have run observation programs. A quick google search revealed this document that looks pretty useful:
In Process Quality Assurance (IPQA) Check Points - Guidelines - SOPs (guideline-sop.com)
I suggest that for any form of observation program (be it QA, safety, management) you need to determine what are critical evolutions or conditions that are worth having an independent "eyes-on" to see how they are going. It is also a good opportunity for discussions with the workers doing the job about barriers, pride, concerns, well being, etc. Similar to the example I provided you need to determine
what is important to observe,
how often / when should the observation be done
determine who is qualified to do those observations,
provide checklists or other information on what the observer is supposed to observe
assign observers to observations
a way for the observer to provide feedback to the worker and QA
a tracking and trending system for were the observations done and what did they find
a connection to corrective action management system to resolve any problems found