Here is an example of how to create a flex container and add some flex items to it:
<div style="display: flex;">
<div style="flex: 1;">Item 1</div>
<div style="flex: 1;">Item 2</div>
<div style="flex: 1;">Item 3</div>
</div>
This will create a flex container with three flex items. The flex property is used to specify the size of each flex item, with a value of 1 indicating that the items should be evenly distributed within the container.

You can also use other CSS properties to control the layout of the flex items, such as align-items, justify-content, and flex-direction.
Using CSS
In Addition to Css You Can Create a beautiful flexbox

<style>
.flex-container {
display: flex;
align-items: center;
justify-content: space-around;
background-color: #eee;
height: 300px;
}
.flex-item {
background-color: #f00;
color: #fff;
font-size: 32px;
text-align: center;
flex: 1;
}
</style>
<div class="flex-container">
<div class="flex-item">Item 1</div>
<div class="flex-item">Item 2</div>
<div class="flex-item">Item 3</div>
</div>
For more information on using flexbox in HTML, you can refer to the documentation on the CSS Flexible Box Layout Module.
To Do List App Mini Project with Code Tutorial