How do you measure and model a space that doesn't have any right angles?

I’m trying to 3D model my current flat, accurately enough to help my partner and I plan some interior projects, small builds, etc. accurately… also just for fun. The thing is that we live in an old warehouse conversion with really wonky angles, almost none of the walls are joined at 90 degrees so I’m having a tough time figuring out what to reference as a starting point.

Looking for any tips on how to accurately measure and model an oddly shaped space!

I would start with the length of one wall and draw circles or arcs with radii that match the adjoiing walls and figure out the other wall from that. If you share the dimensions it would be easier to guide you.

Measure wall lengths and diagonals. Use two adjacent walls and their diagonal to create a triangle either using circular arcs as @DaveR suggested, or trilateration extension (such as mine available from SketchUcation). Repeat for each additional wall, using one of the previous ones and the next diagonal.

Although it starts in SketchUp, this link is drawn in CAD using the techniques of using diagonals and circles as well as direct drawing of lines. The circles and diagonals is demonstrated from elapsed time 05:00 until the end. I find it works well in SketchUp too but I tend to use arcs rather than circles to help with the clean up of the loose geometry after construction.