FBA Multiple SKU packing

After watching the Seller University videos, I still have a question I’m not finding much info on. I have always sent single SKU in a box but now want to take advantage of spare box space by doing multiple SKUs.

Should the items just be “dumped” in the box? I’d like to make the lowely paid Amazon worker’s life easier by putting the different SKUs in a large poly bag or something but obviously don’t want this confused to sell QTY 200 of one SKU as a single item. The total box will have 3 SKUs but close to 1000 items in it total so obviously it’s a lot of tedious work to sort them by hand.