KanjiJLPT N2
Sack

sack, bag, pouch

Mnemonic

The substitute rips off his garment and stuffs it into a sack. Why? A substitute doesn't need fancy clothes—just a big sack to haul away everything the real teacher left behind. He ties the garment-filled sack over his shoulder and walks out.
Additional thoughts
Picture the substitute stripping down and cramming the garment into a burlap sack—absurd image locks the two radicals together. Substitute (代) sits on top, Garment (衣) wraps around the bottom.
Quick recall
A substitute shoves his garment into a sack and hauls it away.

Details

The keyword for 袋 is sack. This kanji refers to a bag, pouch, or sack—any flexible container used to hold or carry things. It encompasses a wide range of bag-like objects, from small pouches and envelopes to larger sacks. The character conveys the general concept of an enclosing receptacle made of soft material, as opposed to a rigid box or container.
On'yomi
たい、だい
Kun'yomi
ふくろ