How to structure Sanity schema for different fields per page?

Perfect! This is exactly what you need - singleton documents are the ideal solution for your use case.

Since you're building a mini-site where each page has unique, specific fields (not repeating blog-style content), you should create a separate document schema for each page and configure them as singletons. This means each page type will only ever have one instance in your dataset.

Here's how to approach it:

Create a document schema for each page with its specific fields. For example:

// schemas/homePage.js
export default {
  name: 'homePage',
  title: 'Home Page',
  type: 'document',
  fields: [
    {
      name: 'heroTitle',
      type: 'string',
      title: 'Hero Title'
    },
    {
      name: 'heroImage',
      type: 'image',
      title: 'Hero Image'
    },
    // ... other fields specific to home page
  ]
}

// schemas/aboutPage.js
export default {
  name: 'aboutPage',
  title: 'About Page',
  type: 'document',
  fields: [
    {
      name: 'companyHistory',
      type: 'text',
      title: 'Company History'
    },
    // ... other fields specific to about page
  ]
}

Configure them as singletons in your sanity.config.js to prevent creating multiple instances. The singleton document pattern requires three configurations:

1. Structure Builder - creates direct links to each page
2. Template filtering - removes these from the "New document" menu
3. Document actions - removes duplicate/delete actions

The easiest way is to use the sanity-plugin-singleton-tools plugin, which handles all this configuration automatically.

Important: Create one instance of each document in the Studio BEFORE configuring them as singletons. Once configured, the UI to create new instances will be disabled.

This approach gives your client a clean, organized Studio interface where they can click directly into "Home Page", "About Page", etc., and edit the specific fields for each page without any confusion about creating/managing multiple posts.