// you need to pass to the slot, as a prop:
// ChildComponent.vue
<script setup>
const data = `
This is the data

I want to get at it.
`
</script>

<template>
  <slot :data="data">
    <div>
       {{ data }}
    </div>
  </slot>
</template>

// then, access them like this, in the Parent component:

// ParentComponent.vue
<template>
  <ChildComponent>
      <template v-slot:default="{ data }"></template>
  </ChildComopnent>
</template>