Calculate the part's projected area and cavity pressure and compare them with the machine's clamp force. A small machine on a large mold will always flash.
Measure the parallelism of the fixed and moving platens at all four corners. A non-parallel platen concentrates force on one side of the mold.
Excessive holding pressure and a late switchover from filling to holding are common causes of flash.
This note is general guidance. For exact settings, the material datasheet and the machine maker's instructions are the reference.