It's not an issue.
Side face will be non-flat because all its vertices isn't on the one plane.
STL exporter will triangulate this face.
But if we want the predictive result then we have to do it "by hand".
![[Image: 08a.png]](https://i.ibb.co/19vxFwB/08a.png)
Three edges (black) should be added.
It divide whole face into the four parts, three of them will be vertical and one with small slope (so it can be printed without a supports).
If that face should be vertical "at whole" we can use "plane cut" operation to get a "straight vertical" section to extrude.
BTW, "negative" slope up to 45 degrees can be 3d-printed without any problems.
Side face will be non-flat because all its vertices isn't on the one plane.
STL exporter will triangulate this face.
But if we want the predictive result then we have to do it "by hand".
Three edges (black) should be added.
It divide whole face into the four parts, three of them will be vertical and one with small slope (so it can be printed without a supports).
If that face should be vertical "at whole" we can use "plane cut" operation to get a "straight vertical" section to extrude.
BTW, "negative" slope up to 45 degrees can be 3d-printed without any problems.