How would i use /fill to fill an area with downward-facing dispensers filled with a bucket of lava?
The correct command for this is:
/fill <x1> <y1> <z2> <x2> <y2> <z2> dispenser[facing=down]{Items:[{id:"lava_bucket",Count:1b,Slot:<slot>}]}
Where <x1> <y1> <z2> <x2> <y2> <z2> refers to the coordinates of the place you want to fill and <slot> specifies where in the dispenser the bucket of lava is stored (0 = top left, 8 = bottom right)