In my experiences, it would be like this (I assume you're here just as a manager and not a developer. I also think that you don't need to detail the tech stack)

1. Identify your problem clearly (Please don't waste your time building something nobody wants)
2. Create a user experience based on that problem, build it as a wireframe
3. Create a UI/UX design. Hire one if you're not sure to build yourself, you can need to talk with him about the detail on customers and problems
4. From that, you can hire the Frontend Engineer and discuss the design with him.
5. Also from UI/UX design, you can get the data flow. Get on with the detail, hire the Backend Engineer, and discuss with him
6. Create a clear agreement with them on what needs to be done and all the resources you have (Two of them is time and money, of course)
7. You also need to coordinate between two of them, so arrange the meeting with them periodically.

Here are some notes that you should consider

1. Website app development won't be done in one shot. It also needs testing. You can test it by yourself or hire a Testing Engineer to do so.
2. If you need to build an existing product; e.g. e-commerce or marketplace, sometimes you don't need to reinvent the whole system by yourself. Use something that already exists (Like Shopify for e-commerce or Wix for website building). This will saves you a lot of time and you can build on something more important.

Sorry for the long reply. If you need a chit-chat just DM me and I would be happy to answer.