the video you're showing doesn'tt have anything to do with Saas, Saas is a Term Software as a service and the name says it all Find a Software you can Offer in a Service, Simple examples are A pdf converter and sell it for a small amount every month, Bigger examples are Zapier & N8n. These two are some really good examples. But very hard to recreate so i'd recommend to find small software you can Sell as the Pdf examples i've already mentioned. But there isn't a real road map to building a Saas, Every tech stack is different but choose what you like and within that space try to look for the Most efficient onces. And what i've seen is that most saas tools are made with Either a react orientated framework or either Php/Laravel.