Box.html

{namespace neos=TYPO3\Neos\ViewHelpers}
{namespace ts=TYPO3\TypoScript\ViewHelpers}
<neos:contentElement node="{node}">
	<div class="box">
		<ts:render path="columnContent" />
	</div>
</neos:contentElement>

NodeTypes.yaml

'Moo:Box':
  superTypes: ['TYPO3.Neos:Content']
  ui:
    group: 'Structure'
    label: 'Box'
    icon: 'icon-columns'
    inlineEditable: TRUE
  childNodes:
    column0:
      type: 'TYPO3.Neos:ContentCollection'

Root.ts

prototype(Moo:Box) < prototype(TYPO3.Neos:Template)
prototype(Moo:Box) {
  templatePath = 'resource://Moodley.WawaschinekAt/Private/Templates/TypoScriptObjects/Box.html'
	columnContent = TYPO3.Neos:ContentCollection
	columnContent {
		nodePath = 'column0'
	}
}