1. Draw a rectangle for the first bar, rotate it 38,5°. It should be longer than the quilt block.
2. Duplicate the bar, rotate it -38,5°or mirror it.
3. Align the 2 bars centered
4. Pathfinder panel: Apply the add function (first icon)
5. Draw a rectangle 8x10. Position it over the X and align it centered.
6. Pathfinder panel: Apply the intersection function. (Third icon)
I guess I'm not clear on what you mean by "a dimensional 'x' ". Do you have a picture or sketch to share.
I can't figure it out. Neither can Google when I search for "quilt pattern dimensional x".
There are many x block variants used for quilts.(Try Google's search for pictures.)
You can the fabric pieces sew together like a mosaic, or on top of a background pattern or you can sew the outlines of the X only. The last two give a somewhat 3-dimensional effect.
This are examples only and a way to draw similar shapes in InDesign. I'd rather draw in Illustrator, it comes with better tools.
Thanks, Fenja, for that explanation!