JavaScriptからFlaskにデータを送る方法

オセロAIのwebアプリを作ろうと考えています．

オセロの手の思考はPythonで行い，画面の表示はHTML, JavaScriptを用いて行う予定です．
そこで，人の打つ手をJavaScriptからPythonのFlaskに送信したいのですが，どのようにすればできるのでしょうか?調べてもFlaskからJavaScriptにデータを送信する方法しか見つからなかったので，教えていただきたいです．

Python3
1from flask import Flask, render_template, request, session, url_for
2import numpy as np
3
4app = Flask(__name__)
5board = np.random.randint(0, 3, (8, 8)).tolist()
6
7@app.route('/', methods=['GET', 'POST'])
8def index():
9    print(board)
10    return render_template('index.html', board=board)
11
12
13@app.route('/play', methods=['GET', 'POST'])
14def play():
15    if request.method == 'POST':
16        play = request.args.get("index")
17        print(play)
18        if play:
19            print(int(play))
20            board[play//8][play%8] = 1
21    return render_template('index.html', board=board)
22
23
24if __name__ == '__main__':
25    app.run()

html
1<!DOCTYPE html>
2<html lang="ja">
3<head>
4  <meta charset="UTF-8">
5  <meta name="viewport" content="width=device-width, initial-scale=1.0">
6  <title>Othello</title>
7  <style>
8
9    .table {
10      position:absolute;
11      top: 50%;
12      left: 50%;
13      margin-top: -257px;
14      margin-left: -257px;
15    }
16
17    .table td {
18      width: 60px;
19      height: 60px;
20      background-color: #ddd;
21      text-align: center;
22      font-size: 3.8vw;
23      cursor: pointer;
24    }
25
26    .list {
27      max-width: 750px;
28      margin: 0 auto;
29      list-style: none;
30      background-color: #fff;
31      padding: 0;
32    }
33
34    .list-item {
35      display: flex;
36      display: -webkit-flex;
37      -webkit-justify-content: flex-start;
38      justify-content: flex-start;
39      border-bottom: 2px solid #ddd;
40    }
41    .list-item > * {
42      width: 50px;
43      padding: 5px 10px;
44      text-align: center;
45    }
46    .list-item *:last-child {
47      -webkit-flex-grow: 1;
48      flex-grow: 1;
49    }
50  </style>
51  <script src="static/js/script.js"></script>
52</head>
53<body>
54  <p id="index">index</p>
55  <table class="table" id="board">
56    {% for col in board %}
57      <tr>
58        {% for row in col %}
59          {% if row == 1 %}
60            <td>●</td>
61          {% elif row == 2 %}
62            <td>◯</td>
63          {% elif row == -1 %}
64            <td>?</td>
65          {% else %}
66            <td></td>
67          {% endif %}
68        {% endfor %}
69      </tr>
70    {% endfor %}
71  </table>
72</body>
73</html>

javascript
1window.onload = function(){
2
3  var $tableElements = document.getElementsByTagName('td');
4  let order = true;
5  let othelloWhte = '◯';
6  let othelloBlack = '●';
7  let othelloColor = othelloBlack;
8  var index_show = document.getElementById("index");
9
10  for (let $i=0; $i < $tableElements.length; $i++) {
11    $tableElements[$i].addEventListener('click', function(){
12      let tableElements = [].slice.call($tableElements);
13      let index = tableElements.indexOf(this);
14      index_show.innerHTML = index;
15      putOthello(index);
16      changeOrder();
17    });
18  }
19
20
21  function putOthello(index) {
22    $tableElements[index].innerHTML = othelloColor;
23  }
24  function changeOrder() {
25    if (order) {
26      othelloColor = othelloWhte;
27      order = false;
28    } else {
29      othelloColor = othelloBlack;
30      order = true;
31    }
32  }
33}