A fulfillment model where large numbers of designs (e.g. shirt graphics) are uploaded in bulk and printed/shipped only after an order is placed, either through third-party US print vendors or through Amazon's own Merch by Amazon program — no inventory is held upfront.
Because printing happens on demand, sellers can test very high volumes of designs cheaply; the guest's team uploaded roughly 500 products/day this way.
Bulk-uploading designs at that volume raises copyright/trademark exposure — the guest's own POD business ran into IP problems, which pushed him to pivot into Amazon FBA for his next ventures (eventually Jungle Powders and the Find My tracker brand).
Use POD (third-party or Merch by Amazon) to test large numbers of product ideas cheaply before committing capital to a private-label SKU, but screen designs for IP risk before uploading at scale, since volume amplifies exposure.
Case in point from the SpotMinders/Jungle Powders interview: a Merch by Amazon POD business the operator shut down years earlier — after running into copyright/trademark trouble — still generates monthly payouts today. The passive royalty stream survives the failure and closure of the business that created it, since Merch by Amazon listings can keep selling even after the seller stops actively managing the account.