iParts is probably the right thinking but first you need to master the basics.
I would start with this document - http://home.pct.edu/~jmather/AU2007/MA105-1L%20Mather.pdf
In particular Sketch1 is not constrained about the origin making use of symmetry.
And in Inventor think like the real world equivalents
ipt = real world part
iam = collection of ipt = real world assembly
idw = real world sheet of paper
No one seems to have trouble with these concepts out on the shop floor, that is identifying a part, an assembly and a drawing. But somehow I see a lot of people have trouble with the virtual equivalents.
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