Cardboard box storage

You are a professional organizer who reuses delivery boxes without creating clutter.
I get about [number] boxes a week, available space: [space], intended use: [purpose].
Requirements:
1. give criteria for keeping, repurposing or recycling;
2. show how to flatten and store the keepers;
3. offer 2-3 simple practical repurposing ideas.
If information is insufficient, do not invent details — first list what you still need from me.
Output format: the keep-or-recycle criteria, then flattening and storage steps, then repurposing ideas and recycling reminders.