With the Thule load bars you can get the outrigger that retracts and extends from the front bar, this allows you to rest the bow on the bar and pick up from the stern.
If factory load bars the best option that I know of is buying a door mat to protect the vehicle, set it above the rear hatch and you can rest the bow on it, picking up from the stern and sliding it across the rear load bar. If you have saddles just tie it down if not you need to step up on the wheel or foot stool and flip over and tie down. Slopes do make loading much trickier
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