Example of how to add a form to every instance of a type of Wagtail CMS Page, without having to manually build the page for each new page in the Admin

article.html

{% extends "base.html" %}

{% block content %}

  <p>(Article content here.)</p>
  
  <p>Send us your thoughts:</p>
  
  <form action="{% pageurl page %}" method="POST">
    {% csrf_token %}
  
    {{ form.as_p }}
    
    <input type="submit" value="Send">
  </form>
  
{% endblock content %}

article_landing.html

{% extends "base.html" %}

{% block content %}

  <p>Thanks for your thoughts!</p>

  <p><a href="{{ page.url }}">Return to “{{ page.title }}”</a></p>

{% endblock content %}

forms.py

from django.core.exceptions import ValidationError
from django.db import models

from modelcluster.fields import ParentalKey
from wagtail.contrib.forms.models import AbstractEmailForm, AbstractFormField


# All of this is so that we can automatically generate a form on every
# ArticlePage, and don't have to create it manually in the Wagtail
# Admin for each one.
#
# This inspired by https://stackoverflow.com/a/47303659/250962


# The fields that will be on the form on each ArticlePage.
#
# field_type can only be one of the following:
#
# 'singleline', 'multiline', 'email', 'number', 'url', 'checkbox',
# 'checkboxes', 'dropdown', 'multiselect', 'radio', 'date',
# 'datetime', 'hidden'
#
# Important: Label MUST be unique in each form
#
# Should be in the correct order for the form:
ARTICLE_FORM_FIELDS = [
    {
        'label': 'Your comments',
        'field_type': 'multiline',
        'required': True,
    },
    {
        'label': 'Your name',
        'field_type': 'singleline',
        'required': False,
    },
    {
        'label': 'Your email',
        'field_type': 'email',
        'required': False,
    },
]

RESERVED_LABELS = [field['label'] for field in ARTICLE_FORM_FIELDS]


def validate_label(value):
    "Ensure we have no duplicates."
    if value in RESERVED_LABELS:
        raise ValidationError("'%s' is reserved." % value)


class ArticleFormField(AbstractFormField):
    """For creating the fields on a ArticlePage's form.
    These are all created in ArticleEmailForm.get_form_fields(), rather
    than in the Wagtail admin.
    """
    page = ParentalKey('ArticlePage',
                        on_delete=models.CASCADE,
                        related_name='form_fields')

    # Redefine 'label' field so we can ensure there will be no conflicts with
    # constant fields
    label = models.CharField(
        verbose_name='label',
        max_length=255,
        help_text='The label of the form field, cannot be one of the following: %s.'
        % ', '.join(RESERVED_LABELS),
        validators=[validate_label]
    )


class ArticleEmailForm(AbstractEmailForm):
    """Extending AbstractEmailForm to add our customm extra fields, so that
    they don't have to be defined afresh when creating every ArticlePage.

    ArticlePage should inherit from this.
    We're putting all the form-related stuff here so that it's kept separate
    from the more general Page-related stuff.
    """

    # Redefine the to_address, from_address and subject so that they don't have
    # to be entered for every new ArticlePage.
    subject = "Comment about an Article"

    @property
    def to_address(self):
        """Get the email's 'to' address. You may want to set this somewhere
        more useful, in a setting.
        """
        return "bob@example.org"

    @property
    def from_address(self):
        """Get the email's 'from' address. You may want to set this somewhere
        more useful, in a setting.
        """
        return "bob@example.org"

    def get_form_fields(self):
        """Add to the parent's get_foro_fields() to add our hard-coded
        field
        """
        fields = list(super().get_form_fields())

        # Append instances of ArticleFormField - not actually stored in the db

        # `insert(0` will prepend these items, so the last added will be first
        for field in reversed(ARTICLE_FORM_FIELDS):
            fields.insert(0,
                ArticleFormField(
                    label=field['label'],
                    field_type=field['field_type'],
                    required=field['required']
                )
            )

        return fields

    class Meta:
        abstract = True

pages.py

from wagtail.core.models import Page

from forms import ArticleEmailForm


class ArticlePage(ArticleEmailForm, Page):
    template = "article.html"
    landing_page_template = "article_landing.html"
  
    # More here...