Layer 2 will be your 'seating' area, so you will want to position all blocks with holes facing front so you have solid surface all the way across.
First row (front) will be 3 full/raw blocks and 2 half blocks. Stagger seams by placing both half blocks on outer ends and full/raw blocks in middle as shown in picture.
Second row will then be 2 Full/Raw blocks and 2 Full/Finished blocks.
Third row same as first.
Fourth row same as second.
Your base is completed at this point and all you have left is the arms and back.