I would like to make a removable USB flash drive from scratch. I would probably start from component selection. And because this is not as exciting as some other DIY projects, I haven't found any reference designs I can follow. Is there a resource you can recommend to find a schematic of a usb flash drive so i can look at it as a reference design
The last of the "easy to find, easy to obtain datasheet" was the SMSC USB97C242. As memory sizes rapidly increased it was obsoleted a few years after its 2002 introduction.
Closest thing to that you will find today is a dedicated USB to SD card controller. USB2240 comes to mind. Use with commonly found SD Cards. You could use a eMMC NAND memory device (which has built in wear leveling) if you wanted to create a custom board and print a custom enclosure.