Step 1: Base
A 3X7 area of slabs.
Step 2: Back
1 block away from where you want the back of the car to be add stairs facing the front, then blocks afterword.
Step 3: Carpet
Add white carpet with a colored stripe through the middle, like in the picture.
Step 4: Windshield
Make a glass windshield.
Step 5: Inside
Break the middle of the windshield, then put a sign there and lower the slab.
Step 6: Wheels
Put the glass back in and cover it with carpet. Then add wheels like the picture(yes there's a third one in back, I'll give you three guesses as to where it is)
Step 7: Bumpers
Add signs around all of the bottom except for the wheels.