How do I deal with the dirham being a closed currency (it can't leave the country)?

The thing to understand up front is what "closed currency" actually means in practice: the Moroccan dirham isn't freely traded internationally, so you can't reliably buy it from a bank back home before your trip, and you're not supposed to export more than a small token amount when you leave. This isn't a hassle so much as a planning constraint — it simply means dirham is something you acquire on arrival and use up before departure, rather than stockpile in advance or take home as a souvenir of cash.

So the workflow is straightforward. Don't waste effort hunting dirham before you fly; you may need a little foreign cash (euros or dollars) as a backup, but you'll get your actual spending money inside Morocco. The best source is bank ATMs, which give near-interbank rates with a fee-free card; official commission-free bureaux de change handle any cash you want to swap. Withdraw in sensible chunks as you go — every few days — rather than one big lump, both for security and because you don't want to be left holding a fat wad of un-exportable dirham at the end.

The real art is the wind-down at the end of the trip. As your departure nears, taper your withdrawals and aim to spend your remaining dirham on the way out — a final dinner, gifts, the airport café, tips — so you leave with little or none. If you do have a chunk left, the airport has exchange desks where you can convert dirham back to a major currency before you fly, but here's the catch travellers forget: you usually need to show the original exchange or ATM receipts proving you obtained the dirham legitimately, and the rate isn't generous. So keep those receipts from the start.

A couple of practical guardrails. Don't change far more than you'll use, and resist a big ATM pull on your last day. A small amount of leftover dirham is no crisis — a few hundred is easy to spend at the airport or keep as a keepsake — but a few thousand you can't convert or export is just wasted money. Plan the closed-currency reality into your trip from day one: source dirham in-country, spend it down deliberately at the end, hang onto your receipts, and the rule becomes a non-event rather than a nasty surprise at the gate.