Take a large bowl, and add sliced coleslaw, capsicum, onions, julienned carrots, and sweet corn kernels. Give it a mix.
Then, add salt, pepper, oregano, red chili flakes, and mayonnaise. Mix them thoroughly till you get a nice coating on the veggies.
Now, take a slice of bread, spread the filling evenly on every corner on one side, and overlap it with another slice.
Switch on the flame to medium, and heat up the griddle.
Apply melted butter on the exposed sides of the bread, and grill it on both sides till you get a nice crispy brown layer.
Your veg coleslaw sandwich is ready to be served.