Step 5: Put the sides together: Screw the side slats onto the legs.
The wood I used was soft and fairly thin, so I had to drill the holes before turning in the screws, otherwise it would crack.
Once you have four screws in each slat, you will want to add two more screws to each one on the front edge of the back leg. (See drawing.) Use the same template to make the marks, considering the edge of the back leg as the side edge. Or, if you are the kind of person who likes to just eyeball it, do that.