You can do something like a reverse range seq
:
{{ $slice := your list }}
{{ $len := len $slice }} <!-- get length of list -->
{{ range (seq $len) }} <!-- see docs -->
{{ $i := sub $len . }} <!-- $i at first iteration will be (len - 1), then (len - 2) etc -->
{{ index $slice $i }} <!-- get list element at $i -->
{{ end }}