I’ve had similar issues my entire life, and successfully overcame and fixed my flat feet through slowly building up a regimen of strategically strengthening and rebuilding the arches of my feet.
This included walking barefoot on the balls of my feet (forefoot) and other exercises strategically targeting these muscles.
My clients have also had a lot of success with these routines.
I’d love to share more!
I see that you have some highly respected certifications and would recommend that you look into another which addresses the very problem you are talking about. It can be done online which, since you live in India, will probably be preferable to you.
I am talking about the level 1 of The BioMechanics Method of Justin Price who has developed a comprehensive and systematic approach to the exact problem you are describing. Here is a link to his website http://www.thebiomechanics.com/what-is-tbmm.asp.
I have taken this course recently myself and highly recommend it.
Sometimes a shoe insole can aggravate the problem of flat feet because they allow the feet to be supported without doing the work. Depending on your exercise routine there are a few ways to help strengthen the feet and ankles. If you like to lift weights, try going barefoot (if your gym allows it or don’t run the risk of dropping anything on your feet) and adding some calf raises to your routine. Walking or running on sand is also a great way to reawaken the feet because the ground will supply very little support. Most yoga classes emphasize the feet being strongly grounded, and you may find that adding a yoga routine to your week will also help stretch and strengthen the ankles, feet, and calves.