Action Example

block.json

[
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "Hiya, it's me, *Erna*. The next lunch date will be next Thursday.\nThat's a tiny reminder 😉.\n\nWanna join and get to know new people?:curry:"
    }
  },
  {
    "type": "actions",
    "elements": [
      {
        "action_id": "notify.prompt",
        "type": "button",
        "text": {
          "type": "plain_text",
          "text": "Join lunch dates",
          "emoji": true
        },
        "value": "hi"
      }
    ]
  }
]

payload.json

{
  "type": "block_actions",
  "team": {
    "id": <ID>,
    "domain": "daheq"
  },
  "user": {
    "id": <ID>,
    "username": "felix",
    "name": "felix",
    "team_id": <TEAM_ID>
  },
  "api_app_id": <API_APP_ID>,
  "token": <TOKEN>,
  "container": {
    "type": "message",
    "message_ts": "1568371037.000700",
    "channel_id": <CHANNEL_ID>,
    "is_ephemeral": false
  },
  "trigger_id": <TRIGGER_ID>,
  "channel": {
    "id": <ID>,
    "name": "directmessage"
  },
  "message": {
    "type": "message",
    "subtype": "bot_message",
    "text": "Hiya, it's Erna!",
    "ts": "1568371037.000700",
    "username": "erna",
    "icons": {
      "emoji": ":knife_fork_plate:",
      "image_64": "https://a.slack-edge.com/80588/img/emoji_2017_12_06/apple/1f37d-fe0f.png"
    },
    "bot_id": <BOT_ID>,
    "blocks": [
      {
        "type": "section",
        "block_id": "Lhs",
        "text": {
          "type": "mrkdwn",
          "text": "Hiya, it's me, *Erna*. The next lunch date will be today at 10:00am.\nThat's a tiny reminder :wink:.\n\nWanna join and get to know new people?:curry:",
          "verbatim": false
        }
      },
      {
        "type": "actions",
        "block_id": "E5RN",
        "elements": [
          {
            "type": "button",
            "action_id": "notify.prompt",
            "text": {
              "type": "plain_text",
              "text": "Join lunch dates",
              "emoji": true
            },
            "value": "hi"
          }
        ]
      }
    ]
  },
  "response_url": <RESPONSE_URL>,
  "actions": [
    {
      "action_id": "notify.prompt",
      "block_id": "E5RN",
      "text": {
        "type": "plain_text",
        "text": "Join lunch dates",
        "emoji": true
      },
      "value": "hi",
      "type": "button",
      "action_ts": "1568371348.485715"
    }
  ]
}