There is a special way to practice mantra at a more deeper level by using your favorite mantra/ishta devata mantra etc and project it into each part of the body and better if you can locate also the marmas point.
This concept is explained into the Nyasa Yoga book of William Bodri and also Mantra Yoga and primal sound from David Frawley. In the first book William Bodri explain how to create the pranic body and shift consciousness from physical body to pranic body as default state. He gives several advanced practices from yoga to qi gong, nutrition etc. Sitting meditation/standing meditation etc. Here I focus on the mantra method. But for now if you can do only zhang zhuang posture on daily basus this is very good for this exercise. I cant give all the sound and beeja, you can get the books and have the full method.
When you do daily Nyasa yoga the energy body become your main body and through it you move the physical one. In other word your consciousness is no longer into the physical but only into the pranic or illusion body. Some yogi use this practice to have amazing abilities and enhance their chance to get enlightenment into one incarnation.
Eastern vampire practicer use the same pranic body to quit the physical one and do predation, become unvulnerable ( this body cant be hurt by any lower being only by higher body) at will and recharge physical so they can have a life span of several hundred of years. Thai acharn of the old school method of Cambodia also learn to recharge the physical body like that
In the Mantra yoga from David Frawley he adds a deeper method to perform the Nyasa practice as he explains how to include the seed mantra sound link to each part of the body directly into your chosen mantra. Your chosen mantra can be any mantra that you use on daily basis.
My advice is to get the mantra siddhi first then do the Nyasa method of sound projection. For example if you use Om namah shivaya chant it 125000 times to get the juice in the mantra. As this is a deity mantra you will gain the benefits link to the deity here Shiva.
Then you can create the energetic body piece by piece. You add the bija sound like that OM ( bija sound) namah shivaya and visualize the corresponding part of the body. Ex for the top of the head Om Am namah shivaya, right eye Om Im namah shivaya etc
You need a qigong/yogic cultivation to give power to this method and in my case I use the wyvern method already given here. I add the kundalini breathing. Other people who like chi kung could use something like flying phoenix chi kung as this one is very good.
I see that some point can be confusing for now, I will come back to get things more clear. If someone wish to try it let me know. As I have said you can use Shiva mantra, Ganapati mantra, Shakti mantra and of course left hand mantra but be careful as they can have violent energy…