堆放 (duī fàng) means “pile up” | MotiTan Chinese Dictionary

More examples

老师让学生把旧书堆放到回收箱里。lǎo shī ràng xué shēng bǎ jiù shū duī fàng dào huí shōu xiāng lǐ

The teacher told the students to pile the old books into the recycling bin.

Items are gathered into a pile and left together in one place.

放fàng: Putting something in a particular place.
摆bǎi: Placing items in a chosen arrangement.

把物品或材料堆在一起放在某处bǎ wù pǐn huò cái liào duī zài yì qǐ fàng zài mǒu chù

堆 (duī, "pile") + 放 (fàng, "put") combines piling with placing, so the word presents objects as a pile left in a particular spot.

In conversation, a simple "put ... in/on" expression is often more natural when objects are merely placed, while 堆放 (duīfàng, "pile up and place") highlights a pile at a location.