Predecessor-completed Ascii Cubes
JavaScript (ES6), 229 bytes



f=
(n,l=n*4+1,r=1,i=n*2,g=a=&gt;` / \\ /
`.replace(/./g,c=&gt;c.repeat(a.pop())))=&gt;n?g([r,,l,--i])+g([r,2,l,--i])+f(n-1,l-1?1:r-4,r-1?1:l-4).replace(/(\S).*(.)/g,r-1?`$1   $&amp;$2$2$2$2`:`$1$1$1$1$&amp;   $2`)+g([r,2,l,,,i])+g([r,,l,,,i+1]):``
&lt;input type=number min=0 oninput=o.textContent=f(+this.value)&gt;&lt;pre id=o&gt;