I use very narrow trim for my dolls. It can be very hard to find trim in the size and colour I need. I frequently make my own trim using a sewing machine, water soluble stabilizer and thread.
On the left of the picture you can see the first stitch I used. Any stitch that goes from one side to the other will work. You can use a zig zag stitch if that is all you have. I then used lines of straight stitches on the each side and 2 rows through the centre of the first row of stitches.
Once the grid was established, I used contrasting thread colours and sewed different decorative stitches over the grid. When I was finished I washed out the water soluble stabilizer and dried the pieces between 2 layers of a cotton towel.
I sometimes also make fabric with the sewing machine. I did this for Sherry so that the colour of the fabric will exactly match tthe embroidered stump.
This piece is a rectangle but you can make specific shapes that will allow you to make clothes with no seam allowance when you ladder stitch the seams together.
After drawing the shape you want (green line) on water soluble stabilizer, use straight stitches sewn close together from one side to the other.