Looking at setting up the ski boots from a lateral alignment perspective, the first thing to look at is the cuff alignment. The cuff alignment can have a large impact on your balance and ability to control the skis. Here is a quick intro into how we approach cuff alignment.
Most performance boots have a cuff alignment ability. The rivets that connect the cuffs to the boot have an oval or offset shape and, by rotating them, you can make the cuffs lean out or in, as needed.
If your boots do not have this option, then there are some other ways to compensate for cuff alignment, but it's best to consult a good boot fitter. In fact, it's always a good idea to consult a good boot fitter rather than mess with it yourself, but here is some basic info on how we check this.
Here is an example of the impact even a simple change on the boot cuffs may have on someone's skiing, a FIS racer not being able to balance to easy balance (note that his boots were "setup properly" by a reputable shop and then fixed by an annoyed coach during lunch break, holding a sandwich in one hand):
The first thing to do is to align the cuffs - using the rivets that connect the cuff (most boots have this, especially race boots). The idea is simple: the cuff must follow the shape of the lower leg, thus the leg must be centred between the two sides of the cuff.
This should ideally be true when standing up but also while the tibia moves forward (i.e. under pressure at the apex). Often, due to the tibia and ankle and in general body alignment, the tibia may move in our out as you flex forward and it changes the influence of the cuffs when gliding versus under pressure at big angles.
In fact, some shapes of tibia make this worse, but that's much more info than we want to address here.
The first step is to check the alignment. Take the liners out of the boots and then take the footbeds from the liners and place them inside the shells. Step inside the shells and find a good position of the foot inside, without toe or heel pressure, so where it would normally be inside the shell.
Then, close the shell to the normal setting, but without using the strap. Now we can check it. It is ideal that you either use a mirror or another person, because you should stand up, balanced in your normal skiing stance.
One check is while standing up in a normal extended stance. Check That the tibia is in the middle of the boot cuff. If it's closer to the inside, then you'll have to tilt the cuff inside and vice-versa.
The second check is to pay attention how things change as you flex forward slowly until the tibia contacts the front of the cuff. Again, check and make a mental note of which side is closer.
The adjustment that you should make should result in the tibia being in the middle, so if the tibia contacts the inside of the cuff, then move the cuff inside.
Once you decide to tilt it inside or outside, take off the boot and loosed up the two screws that hold it in place. Then rotate the oval nut as needed, while observing the cuff tilting:
After adjusting it, tighten the screw and go back to step one and check it.
If you hit the end of the adjustment range and you're still not in the middle, you may be able to find kits with a bigger adjustment range. Otherwise, call your bootfitter for ideas, or contemplate a different boot model.
Here's a good presentation on cuff alignment:
If the boot doesn't have rivets, you can find adjusting kits often. If not, take it to a good shop, see what they can do.
Some boots are "abducted" and this changes how the tibia reacts with the cuff while moving, you may be able to compensate for some foot issues this way.
Some boots have a "rotating cuff", i.e. the nuts holding the cuff in place can be offset and rotate the cuff inside or outside. This may also compensate for same range of motion issues.
References and more info: