This depends on the worktop but we would recommend that you seek professional advice.
A template and fixing clips are provided in the box.
Some circumstances may allow for fitting a bowl directly to the worktop. Alternatively a plywood template can be made to the size of the sink, which will effectively 'sandwich' the sink flange, when addressed to the underside of the material.
We would recommend the use of a sealant between the flange of the sink and the worktop to avoid any water ingress.
In all cases you are advised to consult your supplier.