rustup target add thumbv6m-none-eabi
cargo install elf2uf2-rs
If you just got the PCB from a PCB manufacturer, chances are you can plug in the board directly via USB C and it will show up as a USB mass-storage device, ready for flashing.
If not, hold the "USB Boot" button (near the QSPI chip), and either press the reset button or re-insert the USB cable to put the board in USB mass-storage bootloader mode.
cargo run --release
If you get an error such as:
Error: "Memory segment 0x010000->0x010094 is outside of valid address range for device"
Double check that your RUSTFLAGS environment variable, as it will take precedence over the values set in ./cargo/config.toml.