django Cannot combine queries once a slice has been taken

No. But itertools.chain() will allow you to iterate through both querysets in order.

qiter = itertools.chain(query_set_1, query_set_2)

You can use union() to combine two sliced queryset. Like this:

query_set_1 = Model.objects.filter(...)[:3]
query_set_2 = Model.objects.filter(...)[5:]

queryset = query_set_1.union(query_set_2)