No. Your phone has no flash. Your phone has a led light that pops when your phone takes a photo, and no. It is not powerful enough to be used as a "flash". (A flash is a strobe light of a fraction of a second, let's say 1/500s or faster, and in some circumstances can overpower the sunlight)
Instead of fooling yourself triggering a phone's "flash", learn how to use continuous light illumination.
Yes, you could use your phone to paint light or use it as another light source. Used like this you could use for example a shutter speed of 1/30 and have a decent result.
But probably it is a good idea to use a desk lamp, for example, or some industrial lights that can be cheap (but can be really hot)
But if you really want to take photography that needs a real flash there are some really cheap options. One used flash and a cable, amazon basics flash, or if you want to be serious Yongnuo flashes or Godox with radio triggers are a solid bet.
If you want to make some stroboscopic effects using multiple lights as I am understanding your project:
1) Prepare a completely dark room. Clear any obstacles to prevent accidents.
2) Put your camera on a shutter speed of 30 secs, (probably you need to set up the focus on manual mode) and have some friend to press the button.
3) Take photos with your phone. It will probably shoot some pre-flashes, or something and move around.
4) Again, you could use any other light source to do this kind of photos.