I buy thin fusible jersey for this (found in the interfacing section of JA's and such). I buy it by the yard , and cut into strips. Same as the iron on tape, but much, much cheaper and you can cut the width you need.

i have good success with an edge joining foot and a larger zig zag
https://www.google.com/search?rlz=1C....0.QvHy50aBS8w

I just butt the pieces side by side & zigzag a wide stitch down the length. Works great, you can not tell the batting has been pieced once it’s quilted into the Quilt.

It is a specific stitch usually found on newer machines. It's just like a zigzag but, instead of taking 1 stitch to the right and 1 stitch to the left, it takes 3 stitches to the right and then 3 stitches to the left. The individual stitches are smaller, but the zigzag is still there. It's a way of avoiding "toe catchers" when you need a wide zigzag and makes the zigzag stronger.

I use a glue stick, and overlap the pieces just a tiny bit. You need to let it dry though before using the finished piece.

I do it all the time. I sew a ladder stitch and noone knows it but me. I mostly use hi loft poly batting.

I use the wavy stitch. Almost all my batting is W&M so I do make sure the scrim sides are on the same side.

Edited to add:
I quilt on a long arm so mostly I just butt the two pieces up together and stitch out my panto. I like curvy, swirly pantos and most of my patterns, never go more than 1 to 2 inches without a seam running across it. Everything is stabilized very well. I can never tell where I joined the two pieces together even after many washes.

I love all the wonderful advice here. I am really learning a ton of good, very useful stuff. Up to now, I just stick the pieces together and "zig-zag" them together by hand ... real large stitches. Now, I think I'll try some ideas y'all have here. Thanks!

I just overlap them. Once it's quiltedvyou can't tell.

I zig zag on my machine after butting the pieces together; thread color same as batting. easy peezy.