Complete cases, lightest first. Declarations go in main.rs (for every model) or on the model's ModelAdmin (for one). See Template override for the rules, and the block reference for the keys.

use runique::admin::template::{Block, GlobalBlock, Page};

1. The CSS only: restyle every list's table

The table's HTML stays Runique's. ListTable has a stylesheet in Runique (css/admin/blocks/list.css): yours replaces it, so start from a copy of Runique's.

.with_admin(|a| a
    .templates(|t| t.block_stylesheet(Block::ListTable, "css/admin/list.css"))
    .site(site)
)

/* static/css/admin/list.css: copy of css/admin/blocks/list.css, modified */
.admin-list__cards { gap: 0.5em; }

2. The template only, for one model: the article form's buttons

Only the articles' create and edit forms change; the other models keep Runique's.

fn article() -> ModelAdmin<article::Entity> {
    ModelAdmin::new()
        .templates(|t| t.block(Block::FormActions, "articles/form_actions.html"))
}

{# templates/articles/form_actions.html: included inside Runique's <form> #}
<div class="admin-form__actions">
  <p class="admin-page__subtitle">A saved article is published right away.</p>
  <a href="{{ cancel_url }}" class="btn btn-secondary">{{ cancel_label }}</a>
  <button type="submit" class="btn btn-primary">{{ submit_label }}</button>
</div>

The block is included inside the page's <form>: the CSRF token and the fields are already there, the submit button is enough.

.templates(|t| t
    .global_block(GlobalBlock::Sidebar, "my_theme/sidebar.html")
    .global_block_stylesheet(GlobalBlock::Sidebar, "css/admin/sidebar.css")
)

{# templates/my_theme/sidebar.html #}
<aside class="admin-sidebar" id="adminSidebar">
  <nav class="my-nav">
    <a href="{{ nav.dashboard }}">{{ admin_base_dashboard }}</a>
    {% for resource in resources %}
      <a href="{{ resource.list_url }}"
         {% if current_resource == resource.key %}class="active"{% endif %}>
        {{ resource.title }}
      </a>
    {% endfor %}
    {% if nav.history %}<a href="{{ nav.history }}">{{ admin_base_history }}</a>{% endif %}
  </nav>
</aside>

resources holds only the models the signed-in user may see: no filter to write. Keep id="adminSidebar" if you want the mobile menu button to keep opening the sidebar (admin.js looks it up by that id).

4. A page extending Runique's

To change the articles list's header and keep everything else, the page extends admin/list.html and redefines its Tera block list_header:

ModelAdmin::new()
    .templates(|t| t.page(Page::List, "articles/list.html"))

{# templates/articles/list.html #}
{% extends "admin/list.html" %}

{% block list_header %}
<div class="admin-page__header">
  <h1 class="admin-page__title">{{ resource.title }}</h1>
  <p class="admin-page__subtitle">{{ total }} article(s), newest first.</p>
  {% if resource_links.create %}
    <a href="{{ resource_links.create }}" class="btn btn-primary">{{ admin_list_btn_create }}</a>
  {% endif %}
</div>
{% endblock %}

The page's dev_block blocks (table, filters, pagination…) still follow your block overrides.

5. A whole page on Runique's layout

The page extends admin_base.html: stylesheets, sidebar, top bar and CSRF stay Runique's, the content is entirely yours.

.templates(|t| t
    .with_dashboard("my_theme/dashboard.html")
    .page_stylesheet(Page::Dashboard, "css/admin/dashboard.css")
)

{# templates/my_theme/dashboard.html #}
{% extends "admin_base.html" %}

{% block title %}{{ site_title }}{% endblock %}

{% block content %}
<h1>{{ site_title }}</h1>
<ul class="my-board">
  {% for resource in resources %}
    <li><a href="{{ resource.list_url }}">{{ resource.title }}</a></li>
  {% endfor %}
</ul>
{% endblock %}

With page_stylesheet, the page loads Runique's variables then css/admin/dashboard.css, and none of Runique's other stylesheets. Without it, it keeps Runique's.

6. A standalone page (no inheritance)

No {% extends %}: useful to integrate another frontend tool. What admin/admin_template.html brought must then be written by hand: the CSRF meta, csrf.js (POST actions need it) and the {% csp %} attribute on every script.

{# templates/my_theme/list.html #}
<!DOCTYPE html>
<html lang="{{ lang }}">
<head>
  <meta charset="UTF-8">
  <meta name="robots" content="noindex, nofollow">
  <meta name="csrf-token" content="{{ csrf_token }}">
  <title>{{ resource.title }} — {{ site_title }}</title>
  <link rel="stylesheet" href="{% static "css/admin/my_admin.css" %}">
</head>
<body>
  <nav>
    {% for res in resources %}
      <a href="{{ res.list_url }}">{{ res.title }}</a>
    {% endfor %}
  </nav>
  <main>
    {% messages %}
    <h1>{{ resource.title }}</h1>
    {% for entry in entries %}
      <p><a href="{{ entry.links.detail }}">#{{ entry.id }}</a></p>
    {% endfor %}
  </main>
  <script {% csp %} src="{% runique_static "js/csrf.js" %}" defer></script>
</body>
</html>

Summary

Need	Declaration
Change the colors	theme stylesheet, see CSS theme
Restyle a block	`.block_stylesheet(Block::…, css)` / `.global_block_stylesheet(GlobalBlock::…, css)`
Change a block's HTML	`.block(Block::…, html)` / `.global_block(GlobalBlock::…, html)`
The same, for one model	`.templates(…)` on the model's `ModelAdmin`
Change part of a page	a page extending Runique's (`{% extends "admin/list.html" %}`)
Redo a page	`.with_list(…)` etc., or `.page(Page::…, …)` for one model, with `page_stylesheet` if needed

Admin override examples