Indian Stamp Act, 1899, Schedule I — a Will is not listed among instruments chargeable with stamp duty; other entries (Settlement, Gift, Trust) expressly exclude an instrument that is a Will from their own scope.
Before you begin
Does a Will have to be on stamp paper to be valid?
there's no such requirement. Just print the Will Sanad generates for you on plain white A4 paper — that's good enough.
when you actually sign it, make sure at least two witnesses watch you do it, in person, at the same time. As an extra safeguard, consider video recording the signing too — real evidence if it's ever questioned.
to make it iron-clad, attach a medical certificate from a GP declaring you of sound mind and fit to execute the Will. Registering it helps too. None of this is mandatory — but it's what actually makes sure your beneficiaries get what you intended, without a fight.