There are a few different ways depending on the look ur going for. Either you can use white and black pastels to mix into the color ur using or you ccan create the allusion of shading by pushing lighter and harder with ur pastel.
Some people choose to put different types of food on their sandwiches that you wouldnt normally put on a hot sandwich.
For example if you were going to make a hot sandwich, it would have things like grilled chicken, fish, cooked and hot items.
What do you need help with?