As you can see, slot-based composition is a powerful tool that allows widgets to pull in the page content without cloning or modifying the DOM. . Slots allow to show elements from light DOM in specified places of shadow DOM. When working with Shadow DOM-enabled components, the element is a web platform native way to allow content projection into components. To access children assigned to slots in your shadow root, you can use the standard [HOST]edNodes or [HOST]edElements methods with the slotchange event. This article explains how you can use the and elements to create a flexible template that can then be used to populate the shadow DOM of a. The slotted element appears, but then doesn't disappear when the dom-if becomes false. A slot is a placeholder inside a web component that users can fill with their own markup (see Using templates and slots for more information). Try checking for existing elements in connectedCalback or by listening for slotchange events dispatched by your slot element ([HOST]Root. There are two kinds of slots: Named slots: