In this video I demonstrate how to get a 'waisted' look...
Mmm. 'Waisted' does sound a bit disreputable, as if we're under the influence of something but it's my term for the narrowing waist-like middles of the straight elements and I'm afraid I've never been able to come up with anything better!
I suggest you get some easy-to-carve wood and practise until you get the hang of it.