Step 5 Ensure that all the contents of both layers are centred on the document, and that the lines from the second layer all overlap outside of the document edge. Hit Select All (Cmd/Ctrl + A) and make sure the Line and Fill properties of all objects are transparent.
Step 6 You will need to use the Divide function from the Pathfinder tool (Cmd/Ctrl + Shift + F9) to divide up where these objects cross over. When you are doing more complicated dividing, it’s worth noting that the Pathfinder window has a dialog that allows you to change the level of precision and removal of redundant points.
Step 7 The next step is to fill all of these objects with a seemingly random pattern of colours. Doing this with the current framework will end up with a bunch of irregular shapes in centre of the design that don’t match. For the cleanest look, remove these by selecting them from the centre and deleting.