so the way I did it is with two separate animations:
Draw a 9 sliced image that has the corners and the sides (which should be tileable). Make the center transparent.
Draw an image with pattern mode on, for the center pattern.
Add both as a sprite, with the first one moved a bit up so it’s on top.
On the first image, set the Sprite Renderer tiling mode to Repeat, that way when we extend it, the sides repeat instead of stretching.
Select both images and extend one of the corners using the quad tool to extend the rug.
If the first image’s border don’t reach the edge of the image you might need to make the pattern image a bit smaller.
Does that make sense?