You... don't? You use Arduino for their super good support and documentation while you're building your device. It's only for prototypes. You can buy $4 board

You... don't? You use Arduino for their super good support and documentation while you're building your device. It's only for prototypes. You can buy $4 boards off Aliexpress, but then you have to deal with poor documentation, clone boards, buggy code, etc. I lost 4 days trying to make an SPI screen just "work", until I realized my clone board was outputting the signals offset due to a hardware bug.