Choose your path: buy an allspice-forward blend, or DIY by combining allspice, thyme, garlic, brown sugar, and a scotch bonnet–style heat source.
Use a 1:1 substitution ratio for most rubs; if your substitute is hotter than jerk, start with ¾ and adjust after one taste.
Add the “missing note” before seasoning the whole batch: a tiny pinch of smoked paprika for smoke or extra brown sugar for sweetness.
Let the meat/potatoes sit with the rub for 15–30 minutes so spices bloom (longer is fine for grilling).
For baking, reduce the liquid/seasoning moisture effect by using slightly less rub and adding the rest after the first browning step.