Toast the bread slices on both sides, under the grill or use a bread toaster.
Cut off the crusts, lay the slices flat on a cutting board, put your hand on top of it, and using a serrated knife slide through the bread to split it, or hold it in your hand and cut through it rotating the slice of bread.
If you want, cut these thin slices into a triangle.
Do these above steps while the bread is still warm otherwise the bread will crumble or break.
Then you toast the untoasted sides under the grill until golden.
The sides will curl up; keep your eye on them because this will go very quick.
This can be made well in advance and kept in a tin.