A while back I built a pinewood drafting table for myself. The mechanism works great but I find that papers, books and my laptop sometimes slide down the table. I don’t want to coat the table with a thick paint or a mat because I like the look of the wood. However I am looking for some type of clear varnish or finish that will stop things from slipping (in the same way that some slanted desks have a rubbery surface)
I can hear my instructors now, "Drafting tables are for drafting, they are not dining room tables to be cluttered up with whatever you like!"
Aside from the questionable practice of expecting weighty objects such as books, laptops, etc. to stay put on the described incline, any papers, velums and prints are still affixed with tape when being drafted.
Consider Anti-slip spray. Currently unavailable online here. But I find listings for it at the big box stores. Whether you will use tape or not, silicone is what you are looking for, just take your time applying it in several thin coats.
After that its personal choice whether using a patch of scotch tape is handy for quick sketching.