What we do is create a "variationroot" documenttype/masterpage, that contains only a macro that holds a usercontrol that checks the language of the visitors browser settings and redirects the user to the subsite of his preferred language

Variationroot.master:

<%@ Master Language="C#" MasterPageFile="~/umbraco/masterpages/default.master" AutoEventWireup="true" %>

<asp:Content
 ContentPlaceHolderID="ContentPlaceHolderDefault"
 runat="server">
  <umbraco:Macro
 Alias="LanguageRedirectControl"
 runat="server"></umbraco:Macro>
</asp:Content>

languageredirectcontrol.ascx:

<%@ Control Language="C#"  %>

<script runat="server">
    
        public string DefaultLanguage { get; set; }

        public System.Collections.Generic.IList<string> Languages { get; set; }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            var preferredLanguage = "";
            if (Page.Request.Cookies["preferredLanguage"] != null)
            {
                preferredLanguage = Page.Request.Cookies["preferredLanguage"].Value;
                if (!String.IsNullOrEmpty(preferredLanguage))
                {
                    Response.Redirect("/" + preferredLanguage);
                }
            }
            var cookie = new HttpCookie("preferredLnguage");
            cookie.Expires = DateTime.Now.AddMonths(1);
            var redirectLanguage = "";
            if (Page.Request.UserLanguages != null)
            {
                foreach (string language in Page.Request.UserLanguages)
                {
                    if (language.Substring(0, 2).Equals("nl"))
                    {
                        redirectLanguage = "nl";
                        break;
                    }
                    if (language.Substring(0, 2).Equals("en"))
                    {
                        redirectLanguage = "en";
                        break;
                    }
                    else if (language.Substring(0, 2).Equals("fr"))
                    {
                        redirectLanguage = "fr";
                        break;
                    }
                }
            }
            if (!string.IsNullOrEmpty(redirectLanguage))
            {
                cookie.Value = redirectLanguage;
                Response.Cookies.Add(cookie);
                Response.Redirect("/" + redirectLanguage);
            }

            var defaultLanguage = System.Configuration.ConfigurationSettings.AppSettings["DefaultLanguageRedirect"];
            if (!String.IsNullOrEmpty(defaultLanguage))
            {
                Response.Redirect(defaultLanguage);
            }
            Response.Redirect("/nl");
        }

</script>

The code above also checks if a cookie exists with a user language choice, should he be a returning visitor, it's possible to save the language preference of the visitor should he prefer a different language as his browser preference. This does require additional code for the " language switch" button that you use.

In the content section, we create this structure:

Where we set the locale for the NL and FR pages. All other content is created below these pages (except mayby a custom 404 error, and googlesitemap.xml file for SEO)

For the NL and FR (and other languages) i also set the locale using the "manage hostnames" menu in the context menu of the page:

Detail of the hostname configuration for the dutch version of the website:

The benifit of setting the language this way, is that you can start using dictionary items in your templates and xslt files etc, I also recommend creating a dictionary item "language" with the short keys "en;fr;nl;" in them, so you can test against these columns in xslt in choice statements, to run different queries depening on language