Put the pancake mix, half the butter, sugar, allspice and salt into a mixing bowl and use your fingers to rub it all together until just mixed. Add the oats and stir through.
Spread 1 tablespoon of butter on the bottom of the slow cooker. Add the sliced peaches and pour in the water. Spoon the pancake mix over the peaches and dot the rest of the butter on top. Put the lid on and cook for 4 hours, then take the lid off and cook for another 30 minutes. Serve with a scoop of vanilla ice cream.