mount Blazer::Engine, at: "blazer"

<%= link_to "New Query", new_query_path, class: "btn btn-info" %>

blazer/assets?action=new&controller=blazer%2Fqueries

blazer/queries/new

blazer.new_query_path

class WelcomeController<ActionController

  def index
       redirect_to '/blazer'
  end

end

Add root  'welcome#index'

 mount Blazer::Engine => '/blazer'

mount Blazer::Engine, at: '/'

initializer 'blazer', before: :load_config_initializers do
  Rails.application.routes.append do
    mount Blazer::Engine => '/'
  end
end

main_app.route_path