The pectoral armor is a unique shape, but I took it step-by-step; started with the bat symbol, and then added foamie sheets and built up from there. The process isn't easy to describe, and is best shown in the pictures.
The lower half of the pectoral pieces have a different texture, so I cut up an old handbag I got from the thrift store. I added this texture onto some foam sheets, and glued them on. This is the same texture I would add onto other armor pieces with a similar look, like the abdominal, neck, and bicep pieces. Upon completing the pectoral armor, I saw that it was too small, and yes, I had to completely remake the whole thing over again.
For the abdominal pieces, I traced outlines of the pieces from an image of the suit, cut them out, and then traced outlines on foamie sheets, and cut those out. Again, i added texture from the cut-up handbag for some pieces. I added some extra detail to the lower abdominal pieces by adding a smaller foam pieces underneath to give it a raised details.
I added more detail to the (foamie) straps that connect the armor pieces underneath using an X-acto knife and a wrench. This added lined and ridged texture to the pieces, another good advantage of using pliable foamie sheets.