The book has measurements for more than one size of the pineapple blocks so you do not even have to do the math!!! I totally love that since I am a bit math challenged. Anyway.... you start with two squares the same size. Put them right sides together with the fabric you want in the center on the bottom and sew 1/4 inch seam on all four sides. (You can chain piece these).
Once you have all four sides stitched, make a line from corner to corner on each diagonal on the top fabric.
Once you have both lines cut, press the flaps back. The book recommends using a bit of spray starch. If you stop at this point you have a block called a pineapple chunk. You can sew the 'chunks' together using a 1/2 inch seam.