I don't have my phone yet, but went ahead and ordered these. I have the Samsung clear case and a different case from ebay. When this protector gets here, I'll just stick it in the cutout and see if it fills up most of the area.

I bought the spigen one off eBay thinking it would fill up the whole area. It doesn't. Don't buy spigen unless you want to use their cases.

[2 Pack] imluckies for Samsung Galaxy Z Flip 3 Camera Lens Protector, Ultra Thin Tempered Glass, Anti-Scratch & HD Clear, Easy Installation, Case Friendly Camera Cover for Samsung Z Flip3 5G 2021 https://www.amazon.com/dp/B09FL6ZQD8/ref=cm_sw_r_apan_glt_fabc_DSFXH2YDK08VZW7VDAA1?_encoding=UTF8&psc=1