Just to let you know, I work on a six foot folding table on risers (you know, the kind they sell for dorm rooms). When I first tried this, I was working on a small four foot table (no risers) and basting a queen size quilt (Tesselated Wedding) and this method worked. (I am going out on a limb here when I say this should work for any size quilt on any size table.) Here we go!
First, prepare your quilt top, backing and batting. Press them all well and then fold in half, lengthwise, and press a crease down the center. Be sure this crease is straight, on grain, and very sharp. This will be your registration mark. Lay them on the table and fold/roll them from the bottom to top.
Batting - I use Warm & White or Warm & Natural. Fabric "sticks" to this. My design wall is composed of this batting! See the crease?
Quilt top - The crease is pressed in but happens to run right along a seam. No problem, use the seam instead of a crease.
Lay the batting flat on the table with the center crease in the middle and the folded portion in front of you. Smooth it out, nice and flat. No ripples or creases. Now, lay the backing on top of the batting, right side up, lining up that crease dead on. The top of the backing can be even with the batting, inside the batting or larger than the batting - it doesn't matter as long as that middle crease is lined up. Since I am sure you have sandwiched quilts before, do what you are comfortable with. (excuse the dangling participle, please)
Choose a contrasting thread - one that you can't miss! Use up all those partial bobbins, ends of spools or cheap thread you can't use for anything else. Those 5 for $1.00 spools? If you have any, use those. (You may even decide to buy some next time, specifically for basting, LOL.) Pull out a looonnnggg piece of thread, thread the needle and tie both ends together with a big knot. I put the spool on my sewing machine spindle and pull two arms length of thread.
Use a tailor's basting stitch, start at the top and baste down right along the crease through the backing and batting. Baste only that portion that is flat and smooth - down, usually, about two to three inches from the folded fabrics. Don't pull the stitches tight, just let them lay on top of the fabric. You don't want any tucks or bunches - keep it all relaxed. The length of your stitches is up to you. I fall into a rhythm and find my stitches usually end up about three inches long. You may use a shorter stitch or a longer stitch - whatever is comfortable for you. You won't use all the thread. When you get to the bottom of the prepared portion, just slip the needle in as shown.
Thread another needle the same way. Move over to the left or right of the center, doesn't matter, about six inches and repeat. End the same way. Thread another needle. Move to the other side of the center and repeat. Work this way across the top of the sandwich, switching from one side to the other. If the backing and batting are larger than your table (mine usually are), baste only as far as the sandwich is flat and smooth. Don't worry about the ends yet. Here is what it should look like after the first rows are finished. The red pin is the center basting line. Here is the left side.
Here is the right side.
Don't worry if the lengths are uneven. This actually helps.
Leave the needles in place, move everything up again, smooth and flatten the batting and backing. Starting with the center needle, clip the thread leaving a tail. Rethread that needle, same way, tie a big knot and start another line of basting stitches.
Work the same as the start. Rethreading each needle as you go along.
Until you reach the bottom. Clip your threads. This portion is done. Now you can address the sides. Roll/fold the basted backing and batting back to the top and move it over, right or left, doesn't matter and repeat the process down the sides. You can either work one side and then the other or move the entire roll back and forth. One or two extra stitch lines are all you will need.
How does your back feel? Knees OK? Any questions? Tomorrow we'll deal with the top.
Love from Liri