Here is a pic of mine. My husband used a dremel to cut the holes for the black plastic tube (which is a gutter extension from Lowes $4) after we traced the ends onto the bins where we wanted. This was too easy. Then he used a drill bit to drill the holes for the water bottle nozzle and metal holder. Again, drilling the sterilte box was real easy. We also used the dremel to make a whole for the heat pad power cord to go through and drilled for ventilation holes down low.
So really the whole design is up to you so there isn't a whole lot of instruction to give. But definitely a drill and a dremel are the way to go! We started with a stanley knife but the plastic is pretty thick and it would be clumsy and take a while.