Are you looking to provide a consistent item location for repeatability, a masking product suggestion to protect the item itself while the job is processing or protection for your bed surface? I ask as it is not clear to me by the way you phrased the question.
For simple jigs or pockets to hold items in the same place for repeatability, I have used cardboard with good success. But you can use anything that will provide good depth, easing and speeding item change (replacing the finished item with new).
Masking the item itself is also common to protect the surface from potential residue exposure. I personally use a product used in the signage industry known as ‘transfer tape’. There are several manufacturers of these tapes and the offer a couple of different tac levels as well. These products can be found on the web but can be a tad pricy for some. Plain “Blue” tape works too but can be a bit harder to weed out remaining or leftover tape after cutting.
Protecting the bed…I would again point to cardboard.