Ideal?
1 set angled a little forward, 1 set angled a little back and both sets angled inward a little.
Reality, depends how well you retain the camper on the flatbed. Certainly it can slide backwards, generally, but should definitely be blocked from being able to slide forward at all. And preferably, IMO, sufficiently restrained or blocked from sliding side to side more than the tolerance required to load it (think fender wells in a pickup bed).
Regardless, not rocket surgery and you have experience tieing down and hauling this camper, so use your experience to effect your preferences.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold