Homemade ramps would most likely be built out of 2 x 6 lumber sandwiched together. Each level would need to long enough for your tire to rest on completely. Guessing 6”. 3 levels the bottom piece would be 18” long give or take and 4.5” tall. Maybe add 1.5” per level for a mitre cut ramp. I don’t know about your storage situation but in my Melbourne there is not much left, space wise or weight. My legos in storage take up about the same space as 2 homemade ramps but at a fraction of the weight. I store 20 legos and that gets me enough for the 2 fronts and 2 tires on one side in the rear in most cases.
2016 Melbourne 24K
2013 Sprinter crew cargo SOLD
2002 Toyota MR2 Spyder as a Toad SOLD
2016 Ford Focus set up to flat tow