What you need to get your dog in and out of and how high would make a difference. We use a Petstep folding ramp for our aging 70# Golden. And used it for our previous 75# Golden oldie with bad hips and knees. Get her in/out the back seat of my high 4x4 F350 and in/out of our high 5er. Lifting her 70 lbs is not an option for me any more. Fold ramp and drop in the bed of the truck for travel.
Good folding ramps are not particularly cheap. But if you move around much, a folding ramp would be much easier than something constructed from wood. If the slope is very steep, avoid thin slick carpet for the surface. And, in my opinion, avoid the cheaper plastic telescoping ramps.