Things i would change from that video. I usually prep a few hundred at a time.
Soak longer.
Depending where you pick up your pinecones, spiders and earwigs love to hide inside them.
I like to soak mine in a big garbage bin just for this. I stick the hose in the bin and tumble them around. You can use vinegar or even a little bleach if youre worried when youre ready for the soak. Dead bugs usually float off. I soak with a weighted board on top so the pinecones are all 100% submerged and everything hiding in them is 10000% dead. I have left pinecones overnight to soak. Personally I like them to mostly close up with their soak.
I will then rinse them a bunch more when im done soaking and prep them for the oven.
You can dry them on a screen for a day or so if youre not ready to bake.
Cover the sides of your baking pan with foil not just the bottom. There is where any sap may come off and you dont want that ruining your pan.
I also foil over the top like im cooking a caserole. Were not trying to brown cheese here so we dont need the cones exposed directly, were going to use the oven to dry them sort of. Pinecones can burn easily. Tent the top foil so steam has a direct way to escape.
Watch your oven temps. Pinecones are easily combustable. Many people wouldnt suggest going over 200f.
Im happy with 300.
I have kept mine in the oven, rotating, until they are dry or open.