customise_templates.ex

# Set root layout in pipeline
defmodule MyApp.Router do
  
  pipeline :browser do
    ...
    plug :put_root_layout, {MyApp.LayoutView, :root}
    ...
    
# Set root layout in routes
  scope "/", MyApp do
    live "/dashboard", MyApp.Dashboard, layout: {MyApp.LayoutView, :root}

# Custom live layout in myapp_web.ex
def custom_live_view do
  quote do
    use Phoenix.LiveView, layout: {MyApp.LayoutView, "custom_live.html"}

    unquote(view_helpers())
  end
end

# Use custom_live_view in LiveView
defmodule MyApp.UserLive.Index do
  use MyApp, :custom_live_view
  ...