That is how I join batting together, too.

I am with 117Becca - I cut the batting with nice even sides and butt them together and use the largest zig zag stitch (width wide) and sew them together - much faster than ironing with fusible tape and they hold together nicely and then I hand or machine quilt the final project. Works great for me.

I use polyester high loft batting for 99 1/2% of my quilts and seems I am always having to add a piece. I have made several battings for a double size or a bit bigger quilts. I butt the edges together and sew them together - by hand using a large zig zag, works for me everytime.

I never overlap justy zig zag together. Why buy tape and do both just zig zag.

I overlap the batting edges and cut a long wavy curve through both layers. Then I butt the curves together and use a long wide hand zig-zag stitch. The curved seam is less visible and more secure than a straight one in my experience, and hand stitching doesn't crush the batting any. It only takes a few minutes and works well for me.

This is my method. Works great!

I overlap the batting, then cut a wavy line within the overlapped section. Make sure the peaks and valleys of the wavy line are not extreme so that it is easier to manipulate through the machine as you sew. Separate the two pieces of batting again and remove the wavy scraps. Then abut the two pieces of batting, interlocking the wavy lines. Zig-zag to join the pieces. I find this holds very well and the wavy seam is practically undetectable below the quilt top vs. a zig-zagged straight-line.

I've tried the Tricot but next time I think I will try the wavy line zig zag method. I have a Bernina 649 and it makes a really wide zig zag

I just bump them up next to each other and zigzag stitch...no bump no issues and very easy