Heat the oven to 190C/375F and lightly grease a 9x13-inch baking dish.
Core each apple from the top down, stopping about 3/4 inch from the bottom so the cavity holds the filling without leaking.
Score a shallow line around the middle of each apple's skin with a paring knife, this keeps the skin from splitting as it bakes.
In a mixing bowl, stir together the almonds, oats, softened butter, honey, cinnamon and salt until the mixture clumps together.
Pack the filling into each apple cavity, mounding any extra on top.
Stand apples upright in the baking dish and pour the water or apple juice around the base.
Bake for 35 to 40 minutes, basting once with pan juices halfway through, until a paring knife slides into the center with no resistance and the skins have wrinkled.
Drizzle with extra honey and let apples rest 5 minutes before serving warm.