How to add new elements to a container so that they are indented from each other

I’m weak in the frontend, so I don’t understand what I’m doing wrong, I’m creating a div and inside this div I’m creating span and a, then I add that div to notificationContainer but they are layered over each other, I want them to be stacked on top of each other.

I tried to do a lot of things, but nothing seemed to work.

Screenshot from the inspector

CSS

.notification-block {
  position: fixed;
  bottom: 20px;
  left: 20px;
  width: 300px;
  background-color: #007bff;
  color: white;
  padding: 10px 20px;
  border-radius: 5px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 10px; /* Add margin between notifications */
}
.notification-block a {
  color: white;
  text-decoration: none;
  flex-grow: 1;
}
.notification-block .close-btn {
  color: white;
  font-size: 1.2em;
  cursor: pointer;
}

Javascript

socketNotif.onmessage = function (event) {
  const data = JSON.parse(event.data);
  console.log("Notification received:", data);
  showNotification(data);
};
function showNotification(message) {
  const notificationContainer = document.getElementById("notificationContainer");
  const notificationElement = document.createElement("div");
  notificationElement.className = "notification-block";

  const aLink = document.createElement("a");
  aLink.setAttribute("href", `/chat/${message.chat_id}`);
  aLink.textContent = message.message;

  const spanMessage = document.createElement("span");
  spanMessage.className = "close-btn";
  spanMessage.innerHTML = "×";

  spanMessage.addEventListener("click", function () {
    notificationContainer.removeChild(notificationElement);
  });

  notificationElement.appendChild(aLink);
  notificationElement.appendChild(spanMessage);
  notificationContainer.appendChild(notificationElement);
}

document.getElementById("notificationLink").addEventListener("click", function (event) {
  event.preventDefault();
  window.location.href = "/chat"; // Adjust the URL as needed
});