Hi Daniel,

here is a xml snippet that I use for the purpose you describe:

  <partitioning config:type="list">
    <drive>
      <device>/dev/sda</device>
      <disklabel>gpt</disklabel>
      <initialize config:type="boolean">true</initialize>
      <enable_snapshots config:type="boolean">true</enable_snapshots>
      <partitions config:type="list">

        <partition>
          <!-- BIOS Grub -->
          <create config:type="boolean">true</create>
          <partition_id config:type="integer">263</partition_id>
          <resize config:type="boolean">false</resize>
          <size>8MB</size>
        </partition>

            :

note: enable_snapshots config only makes sense if you are using btrfs on this device.

HTH