I remember designing a tie back in the 80s for Better Homes and Gardens. I used silk and the following pattern stitch went something like this:
CO an odd number of sts.
Row 1: * K1, yarn to front, slip 1, yarn to back; rep from * across,
end k
1.
Row 2: P2, * yarn to back, slip 1, yarn to front, p1; rep from * across,
end last rep with p2.
Rep these two rows to create a fabric that looks woven and lays flat. You can design it so that ends are flat instead of pointed. Start at the wide end and taper as you go. If you can, get dimensions from another tie. When working decreases, be careful to keep your pattern constant.