UPDATE: Made it 2 tiles smaller by combining the output belts into one and weaving them together, you will need a splitter to handle the output.
This is the most compressed setup for an x-ray cracker I could figure out. Simply paste as many of them as you want, input crude oil through the bottom belt from whatever storage you like, flip the middle belts if you don't like the directions, and send the hydrogen and graphite outputs wherever they're needed.
If you pasted more modules than what a mk1 belt can handle, only the central oil, hydrogen and graphite belts will need an upgrade. Upgrading the small belt lines leading into the central input/output belts is a waste of resources, as is upgrading any of the sorters in this setup.