I used thumb tacks. Thumb tacks are flat allowing them to lay against the table top. Put the tacks thru the backing at the points you want to match. You might have to put a small piece of masking tape over the head to keep in in place as you handle it. Tape the backing down to the pinning surface as usual and CAREFULLY smooth on the backing. You can now match up the thumb tacks with the top, again, be very careful. Use lots of pins in the matching areas. I would pin the top as opposed to glue basting as the pins will secure the top to the bottom. Glue basting secures the top and backing to the surface of the batting and if the center of the batting shifts a bit, you will loose the alignment.
This will get you very close, but SITD will probably not be perfect.