9-slice mask on tiled image (2021.3)

Hi all. Thanks in advance for your help.

The goal is a few different vertically scalable UI boxes with different angled corners, not symmetrical, - for example, a box with small angled top corners and a large angled bottom left corner.

2023 supports 9-slice sprite masks, 2021 does not.

Parent w Tiled Background (needs a 9-slice mask)
Vertical Layout Group with 9-slice Frame image
Contents

Any anyone suggest the most ideal / elegant solution?

Thank you!

make a render texture, use readpixels to take a screenshot, then use it as a sprite for the mask