Need guidance- 3d imported part

Good day, I would like to have advice on the best operation to use to machine an angular slot.
I cannot import attachment at the moment to elaborate

you can try the different operations with the animation to see what will work with your tool selection and other pre-sets…perhaps rough, or pocket? Also could make a dummy part to allow for just making the slot.

What kind of slot? What do you mean angular?

This is what I mean by the angular slot.
I would like to understand how to proceed to machine a slot on a 3D MODEL imported in .stl . I would like to machine this slot, but I cannot select anything from the 3D model. Can you suggest a solution please?
Thank you for your help!. Since I am new to this software, I am a bit lost about the options

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May I recommend you start by reading the docs. We have a pretty good overview of each of the operation types at docs.grid.space.