I am a big fan of the Zulu iPad Prodigy cases. Had one with my iPad Air 2, my 1st Gen 12.9 and now for the 10.5. This portfolio case has storage on the back for the Apple Pencil and a magnetic kick stand that lets you prop up the iPad at a number of different angles. It provides good protection and keeps the slim design of the iPP. It is not cheap but the fact that I’m on my third one should tell you how much I like them.
http://www.zugucase.com/ipad-pro-10-5-case-prodigy-x-new-tpu-pc-shell/
http://www.zugucase.com/ipad-pro-10-5-case-prodigy-x-new-tpu-pc-shell/