There are mainly (widely used) 4 types of basins options available for installation in Baths.
1- Over counter Basin (fix over the marble slab, most economical and widely constructed)

2- Under Counter Basin (fits under the marble slab but usually not recommended as dirt accumulates between marble and basin neck)

3- Open Bowl Option (you just place bowl/basin over the marble slab)

4- Pre prepared assembly (on top w.r.t interior but high cost as compared to all, cabinets tend to damage with passage of time if under cabinet material is non-pvc based)
If you ask from me , my personal choice would be 1 then 3rd in terms of economy. If money is no problem then I will simply go for 4th option (PVC based cabinet only and only).
W.r.t frame for options 1 to 3, its being prepared of RCC by leaving hole in advance as per basin type and arrangements. You can further advise your sanitary guy to demonstrate it further for you in terms of practical manner.