i have a specific flame for my right hand, though not for my left one. is there any way i can replicate it using flame forging but having it be specifically for my left hand?

if you have it saved in your stored flame, simply load it up and drag the bodypart slider in the general section to the left hand.
if you didn't mess anything with the gravity & placement parameters, you are probably good to go.
but if you did, usually the one you need to pay attention to is gravity/velocity x, because that determines the direction your flame moves, so you have to adjust it to make it less awkward, depending on the flame.
for example, if your gravity x is set to 40 for right hand, you might want to set your left one to -40 to mirror it and keep things symmetrical.