how easy is it to make a emmc usb?

want to learn BGA wondering if that is a good place to start I do have some soldering experience I have also reflowed a few chips, I have done some SMD work but want to try to make some EMMC USBs as I have seen some blank USB boards on Aliexpress and I would assume I can get the emmc chips there too also got me other questions related to it should I get a stencil and reball it with low melt solder or should I just use factory balls that come solders to the chip