In the past I have worked agile on large international websites and found it lots more fun than any other way of working because as a creative you get to let loose and then simplify it down to what works.
Below is a good way to design for anything digital, large or small...
Uncover
We start by simply talking as a complete team, client, creative, front end development, technical, project management, marketing, everyone. We cover all aspects of the website. The target audience, the tasks people are looking to complete, the information they need and the message the brand needs to get across, the business objectives of the company, the measurements success etc. Basically everything out of everybody's heads. This is a short intense research work before we start thinking about what the solution might be.
Explore
With our target personas, business goals and the rest of the landscape in sight we start broad, sketching everything down on paper and post it notes covering site structure, content, functionality, user flow, wire framing, design style, prototypes. The idea is to cover as much ground as possible so we can get the outlines of everything needed in every area of the website. We build this up layer upon layer, testing key journeys, exploring visual design directions and prototyping any non standard interactions.
Design Alpha
With having gone through the previous stages we can now wireframe with more confidence, testing as we move along the key sections of the site. Deciding what to build now and what to put into future phases so that we are left with a minimal viable product. All the time we are adding detail and content is being refined. Visual design can now start at this phase looking more at the vision for the site, which will be used to guide the more detailed visual design.
Design Beta
With the minimal viable product scoped, visual interaction design and front end development take the lead. With a shared vision the design system and key website pages are designed, brought to life by the front end dev team. Any key journeys are tested with full html prototypes along which then inform the build.
Ship
If the website is a large content managed platform then the content is added and refined using any photoshop templates created to aid the process. Site has been fully tested and now is ready to go live, a good idea at this stage is to throttle the traffic and look at the data delta compared to the current site, iterative amends are made and then throttled traffic is slowly increased to 100%.
Iterate, test, improve
With the minimal viable product live, analytics can be looked at and decisions on the what to incorporate from the ‘future phase’ ideas that we had in the explore and design alpha stages. A good idea is to order these phased ideas by implementing the ideas with the maximum impact with the minimal effort and then testing with real customers before release.