Insert the folium maps into the jinja template

You could save your generated html with folium_map.save('templates/map.html'). Then you can use jinja2 to {% include "map.html" %}. The generated html does not render a map when wrapped in div tags as indicated, if encapsulation is necessary consider using iframes or custom folium templates.

file structure

myapp
├── run.py
└── templates
    ├── index.html
    └── layout.html

run.py

from flask import Flask, render_template
import folium

app = Flask(__name__)

@app.route('/')
def index():
    start_coords = (46.9540700, 142.7360300)
    folium_map = folium.Map(location=start_coords, zoom_start=14)
    folium_map.save('templates/map.html')
    return render_template('index.html')

if __name__ == '__main__':
    app.run(debug=True)

layout.html

<!DOCTYPE HTML>
<head>
  <title>{% block title %}{% endblock %}</title>
</head>
<body>
  <header>{% block head %}{% endblock %}</header>
  {% block body %}{% endblock %}
</body>
</html>

index.html

{% extends "layout.html" %}
{% block title %} Test {% endblock %}
{% block head %} {{ super() }} {% endblock %}
{% block body %}
    {% include "map.html" %}
{% endblock %}

Maybe it can be the solution. First we save a Folium map as an html file on templates folder. Then we create a Flask route to render another html file. On that html file, we create an iframe element that call our map.

Here is the file structure:

proectApp
├── app.py
└── templates
    ├── index.html
    └── map.html

Folium map file (map.html) will be created automatically from my app.py. On app.py I'll create 2 main route: the first one is the home route which will render index.html & create map.html. Then the other is to render folium map (map.html). Here are the codes:

app.py

from flask import Flask, render_template
import folium

app = Flask(__name__)

@app.route('/')
def index():
    start_coords = (-6.1753924, 106.8271528)
    folium_map = folium.Map(
        location=start_coords, 
        zoom_start=17
    )
    folium_map.save('templates/map.html')
    return render_template('index.html')

@app.route('/map')
def map():
    return render_template('7_map.html')

if __name__ == '__main__':
    app.run(debug=True)

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Folium Map</title>
</head>
<body>
    <h1>Render Folium on Flask 🌏</h1>
    <iframe class="map", src="/map" width="600" height="600"></iframe>
    <h3><b style="background-color: lightcoral; color: lightcyan;">
        Render Folium on Flask done!
    </b></h3>
</body>
</html>

The result will be shown on browser like this:

folium on flask

Hope it helps you.