Hi rainbowdragon008, foot mechanics are rarely the result of the foot itself. The way you land and move through the arches of the feet depends a lot on how the spine, hip, knee and ankle move.. and how they might differ from side to side. If one foot is 'flatter' than the other it is most likely that this just shows that the rolling through the flatter foot is really a collapsing of the arch. If that beings to cause local foot issues then the arch supports can help reduce excessive rolling etc. To work on a longer term outcome you need to look higher up the chain and have your therapist assess your gait (the way you walk) to provide some specific insights. Whilst it is possible to alter your movement mechanics in a small way you are unlikely to make longterm sustained/maintenance free changes. It is more a case that being made aware of how it all works and why inserts may be of use that is useful. It is also normal that as you get older you will need modification of your inserts to best match the small variations in an ever-changing gait pattern.

My advice is not to look at these things in too much detail. We are all asymmetrical, we all have subtle compensations in the ways we move. Some understanding/insight into cause and effect and how an assistive device such as an orthotic or even just a change of footwear are very useful tools.

regards
PB