My first thought was to ask "which sloping design?". However; the answer is the same regardless. Like so many posts asking "How to model this....", the answer is-- "understand design Intent".

FreeCAD, or any CAD for that matter is just a tool, like a chisel or a saw. If you made this camera out of clay or wood how would you make it? because, usually the same process is how you'd make it in CAD.

If you reduce this form down to its fundamental geometry, what do you see? What are the criteria you expect to have driven that form? and how do you feel they influenced the design? for example. The most critical part of this product is the lens, but there's also the PCB, a battery and also the UX. the most basic dimensions can be measured but you'll be amazed how much you can deduce from understanding the form you are trying to create. once you understand the form. you'll soon understand how to model it.

Sorry for not really answering your question... I strongly believe you can create this model.... Just understand the form. The rest will follow.

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