The jack will slide under the bike without the blocks. I then sit on the bike, hold it upright and position the jack as I want it. Next, I tip the bike to the right and install the left side adapters, then tip it to the left to install the right side adapters.
Another suggestion to make use of the cheaper jack is to place 2" x 6" blocks infront of the tires, ride up on them, then position the jack.