As you can see in the first picture I have placed a cushion under my paper, that cushion is a small piece of foam. The foam gives your surface a little "give" while stamping and allows full coverage for detailed images.
Another tip is to apply "full even" pressure in the middle of your acrylic block.
I have moved my hands back and forth, carefully, with heavy pressure, I have not had any problem with my stamp block slipping or moving on the paper while moving my hands. That is a different matter if you are stamping on clear card stock or acetate, you don't want to move your hands, just apply even pressure.
Another tip is to have a well inked pad and apply the pad to the stamp rather than the stamp to the ink pad. That way I am assured of full coverage on my image.
It you look at the picture on the right you will see that the image
on the right is lighter in shade. I used my reinker on the Palette Hybrid ink pad, then reapplied the color. As you can see the image came out much more clear and sharp with out any "holidays". That is what it is called when I paint my walls and do not get full coverage, but unlike a stamped image you can put a second coat on a wall. When making a card you want to get it right the first time.
Here is the finished card using a stamp that was exchanged when a customer could not get a clear, even image with it.
Ink; Landscape by Palette
Paper; white card stock from Office Depot & Red Metallic
Misc; red rhinestones