While I can see that making up elaborate flower arrangements for a wedding could be daunting, I do think that most people could have a go at making buttonholes. Its fun and a bit more like jewellery making than floristry.
It also means that you don't end up with those dull rose, fern and sea holly buttonholes that many flower shops seem to go in for.
First you need to choose flowers, get creative and look at seedheads and buds as well as flowers - remember that you can use bits of flowers if the whole is too large. You also need silver rose wires and floristry tape - both available all over the place.
This weekend I was making buttonholes for a wedding where I knew that it would be very hot so I chose seedheads and flowers with sturdy bracts - alliums, siculum, honesty pods and sea holly - rather than something soft like daisies or sweet peas.
Each individual part of the buttonhole needs to be wired - I use a fine rose wire for everything for simplicity sake - you can always use a few strands if its too floppy.
I doubt that my techniques are officially approved - but what you are wanting to do it to replace the stem of the plant with a piece of wire while still supporting it. No-one is going to come and peer at your lapel and judge it - so don't worry.
With things like sea holly I poke the wire up the stem until it comes out the top of the flower. Then I make a hook at the top and gradually pull it back down till it is secure.

Same technique for allium flowers
With something like honesty - I pierce the seedpod and then twist the wire round the stump of stem.
It doesn't really matter how you do it - as long as you end up with everything secure with not too much wire showing.
Then it is just a case of arranging your components together until you like the look of them - here I put eucalyptus and salvias behind sea holly with cut up allium and siculum flowers in front.
Twist all your wires together neatly to make a stem. Cut to length.
Then use green floristry tape - it is slightly crinkly crepe like tape that will stick to itself - cut a length about 20 cm long and, starting just below the flowers wrap it round and round the wire to make a green stem. It will be obvious how to do this when you are actually doing it - all my photos made it look complicated and its not.
And there you are- an interesting buttonhole. Pin it on and be proud.
I would love to bring back the fashion for beautiful buttonholes worn every day - small special things.