Flashing eMMC or Booting from microSD

While Flashing eMMC or Booting from microSD, we need a USB based card reader. Can I use my cell phone instead to have access to microSD?

Has anyone tried? Or you recommend a USB based card reader?
Share if you experienced any problems using cell phone

You can buy them on EBay for about $2.00

IMHO you're complicating things unnecessarily. Just buy a card reader.