Not a silly question at all, jrc3813! The rules are very clear about what can be on the desk and what must be in a sealed ziplock bag under the chair (see the rules here:
https://www.lsac.org/jd/lsat/day-of-test ), but they say nothing about the lap. Obviously, no prohibited items, like a pen or a cell phone, but there's no clear prohibition about keeping things on your lap that are otherwise allowed on the desk.
Seems to me that this is going to be an issue of dealing with the human dimension - the proctors. Some may be very lax and not care, others may be unsure of the rules and overcompensate by being hard cases and enforcing rules that do not exist. Most will probably be reasonable people who will see that you have very little room and that there's no problem with keeping a spare pencil or eraser on your lap.
I think this is probably a good situation for "it's better to ask forgiveness than to ask permission". If your desk is truly tiny and you have pencils in your lap, and a proctor comes along and says "you can't do that", just say "sorry" and then put them on the desk somehow. Follow their instructions, don't fight it, don't cause a disturbance. If you have the room on the desk, use it. If there is an empty desk next to you, use that. Don't give them a reason to think you might be cheating, but don't be afraid to be reasonable in the way you solve that problem if it occurs.
If that approach makes you nervous, then you need to ask up front, before the test begins. You can quietly ask a proctor or the center supervisor when checking in, or you can raise a hand once you are seated and before they start the instructions. I wouldn't wait until they have begun the instructions to interrupt and ask!
I'd just do it. Your results may vary. The rules say nothing as far as I can see, but proctors have a way of imagining rules to fill in the empty spaces where doubts live.
Good luck!
Adam M. Tyson
PowerScore LSAT, GRE, ACT and SAT Instructor
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