This split ergo layout follows my preferred split 3x6 + 3 thumb keys (Crkbd) layout with a few changes:
There's an optional number row at the top of the keyboard. I am quite used to using layers for numbers and symbols, so in practice this goes unused.
The dedicated Hyphen/Underscore and Equals/Plus keys on the number row are placed in the same positions as on the ErgoDox EZ. (There's no real reason for this; I just had to do something with those keys.)
The extra thumb keys on the bottom row are used for a Left Alt key (for easier Alt+Tab, Alt+F4, etc.) and a dedicated Super key.
The harder-to-reach thumb keys below the controllers are bound to browser back/forward navigation keys.
(KLE)
(KLE)
(KLE)
(KLE)