Download or clone the `qmk_firmware` repo and navigate to its top level directory. Once your build environment is setup, you'll be able to generate the default .hex using:
```
-$ make lets_split-rev2-default
+$ make lets_split/rev2:default
```
You will see a lot of output and if everything worked correctly you will see the built hex file:
```
-$ make lets_split-rev2-YOUR_KEYMAP_NAME
+$ make lets_split/rev2:YOUR_KEYMAP_NAME
```
If everything worked correctly you will see a file:
Flashing
-------
-From the top level `qmk_firmware` directory run `make KEYBOARD-SUBPROJECT-KEYMAP-avrdude` for automatic serial port resolution and flashing.
-Example: `make lets_split-rev2-default-avrdude`
+From the top level `qmk_firmware` directory run `make KEYBOARD:KEYMAP:avrdude` for automatic serial port resolution and flashing.
+Example: `make lets_split/rev2:default:avrdude`
Choosing which board to plug the USB cable into (choosing Master)