Our new vacuum cleaner motor was slightly larger than the old one and suddenly no longer fitted under the table and sofa. So I printed a raiser, to increase the height, so that the new robot could vacuum under the sofa and table again.

I also took this as an opportunity to work with scad. As the model is very simple, I used this as an exercise.
Maybe someone else has a need for a table, sofa or whatever raiser.
You can choose a round or rectangular shape, as well as the dimensions (width and length for a rectangular shape) or diameter for a round shape. The wall thickness can also be adjusted. This modell can be adjusted to raise anything with a round or rectangular shape.

When setting the dimensions, remember to include some tolerance so that the part fits (measured dimension plus approx. 0.2 mm).
Depending on your circumstances, I would choose at least 4 wall loops and not too little infill, so that the part is strong enough. Also consider using a suitable material. I used PETG and it works with no issues.

After printing simply slide the raiser over the table leg.