<product-card>Пенал</product-card>

<product-card>
  <template shadowrootmode="open">
    <p>Изолированная карточка</p>
  </template>
</product-card>

<template shadowrootmode="open" shadowrootdelegatesfocus>…</template>

<template shadowrootmode="open" shadowrootclonable>…</template>

<template shadowrootmode="open" shadowrootserializable>…</template>

<template shadowrootmode="open" shadowrootslotassignment="manual">…</template>

<template shadowrootmode="open" shadowrootcustomelementregistry>…</template>

<product-card>
  <template shadowrootmode="open">
    <p>Товар: <slot name="title"></slot></p>
  </template>
  <span slot="title">Пенал</span>
</product-card>