Use the QMK configurator, https://config.qmk.fm/#/planck/rev6/LAYOUT_ortho_4x12
To make all the keymaps and layers that you want. The "layout" drop-down allows you to change the layout to meet your specific board layout.
After you are done customizing the layers and keymaps, export the .json file so that you have access to it later. You can import .json files into the QMK configurator to edit them (in case you made any mistakes with your keymaps).
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After you hit "compile" on the upper-right, wait for it to process. Download the firmware with the button on the lower-right. To flash this firmware onto your Planck, use the QMK Toolbox.
Hopefully this mini-guide helps a little bit. Feel free to reach out to me and ask questions.
erickongI have I believe Rev 2 Planck, but I can't flash with new keymap, always says no device. I installed the driver with Zadig, any idea whats the issue? Is selecting LAYOUT and KEYBOARD on qmk tool important?
erickongYes, in the toolbox where I should load the .hex file and then hit reset, then after hitting flash, the console spits out the no device error. I can't remember exactly which rev my planck is... I joined that drop back in August 2015, probably even the first run for all I know but I can't find a way to check which rev I have to save my life