I ordered this and phone lays flat.
https://www.amazon.com/dp/B089CPVHJX/ref=cm_sw_r_cp_apa_i_UUYpFbHV8ZRTP
I have this case and it makes the phone flat on the camera side:
https://www.amazon.com/Spigen-Tough-Designed-Samsung-Galaxy/dp/B089CPVHJX/ref=sr_1_2?dchild=1&keywords=spigen+tough+note+20+ultra&qid=1599193237&sr=8-2