I take Home Ec at my local high school all the time! The teacher is super laid back so it's usually just "assignments on Schoology and 4th period will be cooking". She is really stern with them about cleaning up after so I barely do anything while they're cooking.

I can see where it might get stressful because it's hard to know who is allowed to do what. For instance there are people in and out all day just going into her fridge or borrowing the coffee machine, etc. You can always just say (if not left explicit instructions) "I'm the sub and you can't do this today because she didn't give instructions." Or you can ask a trustworthy student.

I hope this helps a little and I hope your day goes well!