The Kite Publisher Javscript plugin lets you add one-click trade buttons to your webpage. It works like a basket + payment gateway where a popup opens and guides the user through a trade, and lands the user back on your webpage.
If you have already obtained an API key, you can get started immediately by referring to the documentation. Otherwise, you can signup now and get your API key.
Buy a single share of RELIANCE
Sell a single share of SBIN
Trade a basket of multiple stocks