noun
helping oneself; arranging to suit oneself
Often used for serving oneself food or taking liberties in arranging things without asking. Can imply self-serving behavior.
飲み会では手盛りで料理を取り分けてください。
At the drinking party, please help yourself to the food.
彼の計画は手盛りで、他の人の意見を聞かなかった。
His plan was self-serving; he didn't listen to others' opinions.