When the rig is sitting on a solid surface the jack can be placed under the spring or under the axle tube very close to the spring. The problem you may have is that the other tire may be sunk into the ground. If so you may need to lift too far on the axle which has the flat which would be like trying to lift all the weight of that side of the rig with one axle.
When on hard surfaces and lifting under one axle the dog bone will pivot as that axle rises and the tire has clearance to fit on the studs. Do you picture what I'm saying? If the other tire is sunk in, you may need to lift equally under both axles or at the frame in front of the axles. Just thought I'd mention it since it's common when sitting in yards instead of driveways.