Fifteen years ago, PCB houses happily sectioned boards if I sent them a CAD file of it. I don’t know what they do ‘today’ because I’ve made my own boards since (via CNC). However, the approach is the same and I now do it in Fritzing.
Using Inkscape (or any drawing app) there is no need to go through the hoops of making layers. When ‘Loading’ the file into Fritzing, you can ignore the messages - the board loads fine and exports as normal.
A picture being “worth a thousand words”, you can glean from the image what’s going on. Fritzing file attached. They provide the concept… Also attached is the SVG with extension changed to fzz (for uploading).
Many ways to section it - this is simply one way…
panel.fzz (1.6 KB)
the_SVG_panelized1p.fzz (3.4 KB)