MTS

It won't open to lie flat as you'd have a concave sewn to a concave curve, and a convex to a convex.

Ask me how I know this.
And after I did it I just sat there and laughed at myself.
It was one of those "moments."

You need to cut them with wide seam allowances overlapping, RIGHT sides up on both pieces (I know they're batiks but it has to be the final UP side).

Then you can put RIGHT sides together and sew them after you've cut the curves.

As long as it's a nice gentle curve, you won't need a template.
Just work slowly as sew the strips together, don't get ahead of yourself, keep making sure the convex and concave are mostly lining up, and you should be able to press the strip set flat.

Also, cut the strips wide enough so you have room for the curves on both sides.
I work in pairs, then sew the pairs together, then quads together, etc.

You won't need pins or a special foot.

You can square the whole thing up when you're done.