There are a couple of ways you can do it. One is to do some of your long endurance rides on fat tires, doing your best to keep the intensity low. Another (not mutually exclusive) way to do it is to selectively adapt some of the higher-intensity rides to off-road terrain. In that case you wouldn’t worry too much about the exact structure but instead try to accumulate the same volume on riding at higher intensities over the course of the ride (mostly on climbs).