Does anyone know of a personalized abdominal/lower back workout routine? (purely free weight)?

I’m curious about any workout routines pertaining mainly to the lower abdominal and low back regions of the body. Also routines concentrating primarily on free weights exercises would be the most helpful. I currently have a 6 pack, but I’m looking for more definition and on a side note, an increase in pectoral size (the right way). Thank you for any and all input on the matter.