This example demonstrates a "CustomCard" that has a root container and a "Title" slot, both of which can be overridden via the theme or props.
import React, { forwardRef } from 'react';
import { styled, useTheme } from '@mui/material/styles';
import clsx from 'clsx'; // Standard for merging classNames
// 1. Define Styled Components (The "Slots")
const Root = styled('div', {