Disclaimer: I’m very new to Blender.
I’ve loaded in this image as a reference to essentially trace by deforming a plane:
My best result so far has been by subdividing the plane with loop cuts, deleting unwanted vertices and edges, and dragging the remaining vertices to line up with the reference's edges. But I'm not sure how to get the vertices to align properly with a curve modifier. I've tried grouping vertices and applying a curve modifier to them, but I keep getting the corners of the mesh flipping over themselves.
I've also tried wrapping the plane in a lattice modifier, and tracing free hand with a Bézier curve.
End goal is to extrude, bevel corners, and export as stl.
Edit: adding image of best attempt, edges are more jagged than desired (I also messed up the rotation of the reference)
and highlighted faces from @moonboots response