I have a middleware that validates if the person verified your email, which works perfect because if you did not verify it, it returns it to your home.
How can I add an alert message once it is redirected that says you should verify your email, can you use flash session?
Yes, that's the "right" way to do it according to Laravel:
In the middleware:
$request->session()->flash('mensaje', 'Debes verificar tu correo');
return redirect('/home');
On the controller that receives the redirection:
$mensaje = $request->session()->has('mensaje') ? $request->session()->get('mensaje') : '';