Part of the screen has vertical scroll. How to achieve this?

Hi,
I want to have a fixed portion at the top of the screen and want the rest of the screen to be able to scroll (contains a list item). When I add two columns inside the main scaffold, I keep the top column fixed and botton column scrollable, then I get an overflow error for the main scaffold column as it thinks that content is going outside.

Is there an easy fix to this?