Infrared saunas hide most of their complexity behind flat wall panels, and every one of those panels has wiring running to a heating element that only makes sense if it goes back in the exact same spot. Numbering panels before teardown is not optional here, it is the entire plan.
Pro tip: Take a short video walking around the interior before disassembly narrating which wall is which, in addition to photos; it is a faster reference than scrolling through still images later.
Watch out: Never open panel wiring without confirming the breaker is off or the unit is unplugged; some models retain capacitor charge briefly even after power is cut.