Recently I pieced this utility/throw/snuggle quilt for my eldest son.

Piecing...on the longarm.

Laid out over the quilting machine

Lighting muted to show quilting texture on top

Back Side -- Sample of the Freehand Quilting Textures
Once I finished piecing the quilt on the longarm, I used the long rectangular strips as “freehand practice blocks,” doing something different in each strip/rectangle.
I have received numerous requests for how to do the piecing on the longarm. What I am able to provide by way of free instruction is limited to text description.
TERMS OF USE: This basic process is presented “as is” and does not constitute any type of warranty or guarantee for your outcome. If you choose to use my process, you agree that you are using it at your own discretion, at your own risk and that you alone are responsible for your results.
My basic process for piecing on the longarm:
Backing fabric loaded on the longarm.
Quilt batting loaded on top of backing fabric.
Begin piecing top (on top of the batting & backing). Personal side note: My favorite thread to use for piecing on the longarm is Superior So Fine.
Select a variety of strips, allowing two strips (same width of strip, but differing lengths) per row. By having differing lengths, the center/off-center joins of each row will be staggered.
For each 2 strip (per row) section, I pressed the short, raw edge of one strip under (to the wrong side) 1/4″ — this is what will form the join in that row.
FIRST ROW: Lay fabric pieces right side up on top of batting, placing the pressed short edge of the one strip over (overlapping) the other strip’s raw, short edge by 1/4″. This is the row’s center (off-center) join. It can be be off center or wherever you want but please make it a DIFFERENT place in each row to eliminate bulk build up at the joins. Secure with a few pins. Turn on channel locks of the longarm. Stitch across the top edge of the pieces making sure not to hit any pins and going at a slow pace, smoothing as you go. You may wish to remove the pins as you go or after you have finished stitching across the row. Once you get to the other side of the row, turn off the channel locks, go back to the center join and topstitch the pressed edge (center join). Pull up the center join/topstitching threads as necessary, as you go. I like to tie them off and bury them as I go using a Spiral Eye Needle.
ALL REMAINING ROWS: Row by row, lay the two strips wrong side up on top of the previously stitched row with the pressed short edge on the bottom and raw short edge on the top at the “off center” join. The raw short edge should overlap the pressed edge by 1/4″. Place a few pins across the strips (out of the way of the stitching line) to keep the strips from shifting during the stitching process. Channel lock stitch 1/4″ (long raw edges) across the width of the quilt. You may wish to remove the pins as you go or after you have finished stitching across the row. Once you get to the other side of the row, turn off the channel locks. Bring your iron over to the longarm. Press the long seam all the way across to set the seam. Open and press the new row forward, toward you and on to the batting so that fabric is now right side up and the next row is formed. Bring your longarm back to the center join and topstitch the pressed edge (center join). Pull up the center join/topstitching threads as necessary, as you go. I like to tie them off and bury them as I go using a Spiral Eye Needle.
Repeat as often as needed until the quilt reaches the length you desire, advancing your backing & batting on the rollers as necessary.
LAST ROW: Stitch 1/4″ from bottom edge.
Keep in mind that the piecing/stitching also acts as quilting and it is visible on the back (as rectangles).
Now go back and fill in all those rectangles with lovely freehand quilting!
Happy stitching.
About this technique: I am NOT the first to “piece” a quilt on the longarm. I learned the basics from Deb Levy through her videos available to “Premium (paid) Members” at MQ Resource.  HOWEVER, my method is not exactly the same as hers. Additionally, Deb stated in the video that piecing on the longarm was not original to her. She did not say who was first, nor do I know who was. Further, what I learned from Deb did not involve the center/off-center joining strips together within the rows. She demonstrated the sewing of single strips which were complete rows themselves. I don’t know if others have done the ‘join’ or not. Certainly, someone out there may very likely have thought of it. But no one ‘taught’ that part to me, nor did I ever see, hear, read about how to do it. It was just something I thought to try when I was trying the basic technique and it worked for me.