All that is required for a valid will is a signature by the testator (the person making the will) and the signatures by two attesting witnesses.
So yes, you can write your will on a piece of paper and get two witnesses to attest it, and it would be a valid will (provided that the bequests are legal).
Courts have recognized even holographic (handwritten) wills.
There is no requirement for having the will made on stamp paper, or registered or notarized.
However, wills fall within the instruments that may be optionally registered (Section 18 of the Registration Act, 1908). Wills are registered as a method of proving the authenticity of a will. The reason for this is that the Registrar of Sub-Assurances (the relevant authority for registration of documents) is required to satisfy himself that the person depositing the will is actually the testator (or his agent). This reduces the chances that the will may be challenged as being a forgery. However, other challenges to a will as being signed under the undue influence etc. are still open. The other advantage of registration is that the will is in safe keeping at the office of the Registrar. The will may only be withdrawn by the Registrar by the testator or his agent during his lifetime. On his death, the Registrar may permit an applicant to take a copy of the will. However, the original will is still kept in the deposit with the Registrar. This ensures that the will has not tampered with subsequent to the testator’s death.
However, a testator is entitled to revoke or change his will any time during his lifetime. Therefore if the testator makes another will after the registered will, such subsequent will shall prevail over the first, even if the first will is registered and the subsequent isn’t.