Here is how I added extra height and stability to my car's scissors jack. I have always found it useful to have the jack lifted closer to the car chassis before operating the jack.
Step 1: Drilling Mounting Holes.
I made 4 holes onto the flange feet of the jack. These will be for wood screws later on.
Step 2: Attaching a Base Block.
I screwed on a piece of 2x4 wood block to be the new base for the jack.
Step 3: Additional Base Plate and Completion.
I put a larger wooden base for added stability to prevent the car rocking off the jack while lifted. Now the jack is much more useful and a little safer to use.