Compile the firmware by running

Make

The SKR3 doesn't have a bootloader so you cannot flash it from the RPI. You'll need to use the SD method.

Open WINSCP

Navigate to /klipper/out/

Copy klipper.bin to your PC and rename it to firmware.bin

Copy firmware.bin to a SD. I used a 128mb one I had laying around

Holding the RESET button on the SKR3 EZ, insert the SD card into the SKR3 EZ.