On bottom of both bread pieces brush on olive oil.
Spread one tablespoon of pesto (or more if you like) on each piece of bread on the top side. So the bottom will have olive oil and the top will have pesto.
On the the pesto side on ONE HALF of bread place spinach leaves. Repeat with other bread.
On top of spinach place 1/4 of mozzarella. Repeat with other bread.
Layer on chicken, olives, tomatoes and 1/4 of mozzarella. Repeat on other bread to make two complete sandwiches. Fold in half with the olive oil side on the outside.
Grill on panini press or Foreman Grill.
If you don't have these (as I don't) heat grill pan to medium heat. Wash two bricks and cover with foil. Place sandwiches side by side on grill pan. Place foil covered bricks on top. Cook on medium for 4-6 minutes. Turn over and replace bricks. Cook an additional 4-6 minutes until cheese is melted and bread is toasted brown.