Should I stand with my legs aligned with my shoulders and the boot sole should be completely on the strait floor?
Canting is done under the sole of the boot by tilting the boot shaft---aligning the knee over the ski---or moving the ski to a flat position under the leg. We are generally setting folks up at hip width( about 4.5 inches apart between boots) to ski a flat ski with knee over or just inside ski center, this position moves around depending on the skiers preference. Ultimately you do want to have a flat ski (no edges engaged) (no "A" frame).
There is a lot more that goes into alignment than just canting---foot beds (control ankle position), cuff adjustment (improperly called canting by boot manufacturers), fore/aft balance position controlled by the forward lean of boot cuff and size of calf muscle, boot board angle, binding heel/toe differential (called, delta angle).
The biggest thing you need is experience---which comes in the form of a very experienced boot fitter/alignment specialist. there are probably only a few fitters/shops qualified (nationally) capable of setting you up. Check the "Who's who" section on here to find someone nearby, who is capable.