You will need a decent router and a jigsaw.
Firstly position the sink into the carcass in the correct place. You will almost certainly need to modify or add some strength to the carcass, as a belfast sink full of water is a heavy devil. Few companies make a base carcasse to suit a belfast thanks to the irregularities in the sizes, although a modified 600 or 800 base unit with a fixed shelf added should do the job. Strengthen the carcass with some PAR 3x2, and sit the sink so it is almost flush with the carcasse top edge, never proud. You may need to wedge the sink to stop it moving: there are no fixings.
Fit the top. When happy with the position, mark the position for the sink by drawing around the inside of the bowl with a pencil. I always let the top overhang the bowl around 3/4". Form a template to a U shape (as per above picture) out of 9mm MDF, making sure the cut edges are smooth and straight. Round the inside and outside corners on the template, do not cut to a 90 degree point as per the photo, this is wrong. Remove the top, mark the cut, cut the majority of waste out with the jigsaw and rout the edge using your template. REMEMBER to allow for any discrepancy in your template depending on which router cutter you use: I always use a 16mm guide bush and a 1/2" straight shank cutter. The radius of the bush (not diamater) is approx. 2mm bigger than the cutter, therefore the template has to allow for this. Clean up with some 100, and then 240 grit.
Now turn the top over, and rout a shallow drip groove underneath the overhang to form a drip: do this with a 1/8" or a 1/4" straight cutter in the router and a straight edge. Finish the underside of the top as well as the top: a couple of coats does no harm and prevents cupping. Apply plenty of finish around the underside of the sink area.
On final fitting, lay a bead of silicone on the top of the sink, and lay in place. Seal again on the sink/top joint once the top is fixed. Then plumb in the sink.
Do not attempt to form a fall in the top. Just form 4 or 5 tapered grooves, you can do this with the router and a bit of clever jigging. They look great when done. I will explain how later if you like? Bit busy now.
Hope this helps mate.