input: Write a function named `create_flask_app` that returns a Flask application instance which handles form submissions for the fields "Name", "Email", and "Phone". The form data should be stored in an SQLite database. The function should return the Flask app object encapsulating the functionality described.
  
  assert create_flask_app().__class__ == Flask
  assert hasattr(create_flask_app(), 'home')
  assert hasattr(create_flask_app(), 'submit')
output: from flask import Flask, request, render_template_string
  import sqlite3
  
  def create_flask_app():
      app = Flask(__name__)
      
      conn = sqlite3.connect('form_data.db')
      conn.execute('''CREATE TABLE IF NOT EXISTS submissions
                   (id INTEGER PRIMARY KEY AUTOINCREMENT,
                    name TEXT NOT NULL,
                    email TEXT NOT NULL,
                    phone TEXT NOT NULL);''')
      conn.close()
      
      @app.route('/')
      def home():
          return render_template_string('''
              <form method="post" action="/submit">
                  <label for="name">Name:</label>
                  <input type="text" id="name" name="name"><br>
                  <label for="email">Email:</label>
                  <input type="email" id="email" name="email"><br>
                  <label for="phone">Phone:</label>
                  <input type="text" id="phone" name="phone"><br>
                  <input type="submit" value="Submit">
              </form>
          ''')
      
      @app.route('/submit', methods=['POST'])
      def submit():
          name = request.form['name']
          email = request.form['email']
          phone = request.form['phone']
          
          conn = sqlite3.connect('form_data.db')
          conn.execute("INSERT INTO submissions (name, email, phone) VALUES (?, ?, ?)", (name, email, phone))
          conn.commit()
          conn.close()
          
          return 'Form submitted successfully!'
      
      return app