The mcslck repo contains a fritzing sketch suitable for homemade pcbs, for a shop to make them they might need some refining. The mchckduino repo provides a patch and a few scripts (with working installer) that makes teensyduino able to compile and upload arduino sketches for mchck (and mcslck) boards.
1. Comment out the SCB_VTOR = 0; line in mk20dx128.c
2. Change the origin (to 0x00000c00) and length (to 128K-3K) for the FLASH, in mk20dx128.ld
3. You should also comment out the flashconfig portion of SECTIONS as well since it is not needed.