Launch your fireworks safe from a bottle.
But stabilise the bottle with these customizable arms.

I do not fire any fireworks, but hopes that my neighbours do it safely and do not burn down my house ;-). So I have not printed it.

Set the right parameters for the width of the bottle and determine the correct length of the arm.
The arm even have a M4 nut holder to stabilise the bottle even more on uneven roads. Or use the hole to mount it stirly to the road/field.
Use 3 or 4 arms for your bottle and mount them together with a tiewrap.