Steps:

• Have a login route accept a next parameter
• Define your model view and admin index view
• Register models

In the example below, auth.login is the login route. See this article for how to set it up. The snippet below is taken from the Shopyo web framework

from flask_admin import Admin
from flask_admin.contrib import sqla as flask_admin_sqla
from flask_admin import AdminIndexView
from flask_admin import expose
from flask_admin.menu import MenuLink


class DefaultModelView(flask_admin_sqla.ModelView):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def is_accessible(self):
        return current_user.is_authenticated and current_user.is_admin

    def inaccessible_callback(self, name, **kwargs):
        # redirect to login page if user doesn't have access
        return redirect(url_for('auth.login', next=request.url))


class MyAdminIndexView(AdminIndexView):
    def is_accessible(self):
        return current_user.is_authenticated and current_user.is_admin

    def inaccessible_callback(self, name, **kwargs):
        # redirect to login page if user doesn't have access
        return redirect(url_for('auth.login', next=request.url))

    @expose('/')
    def index(self):
        if not current_user.is_authenticated and current_user.is_admin:
            return redirect(url_for('auth.login'))
        return super(MyAdminIndexView, self).index()

# further in app.py
admin = Admin(
        app,
        name='My App',
        template_mode='bootstrap4',
        index_view=MyAdminIndexView()
    )
    admin.add_view(DefaultModelView(MyModelHere, db.session))
    admin.add_link(MenuLink(name='Logout', category='', url='/auth/logout?next=/admin'))