Put in a shaker with half a cup of crushed ice, shake well and put in a Tiki mug - I guess a 14-16 Oz one , add crushed Ice to fill. Garnish with, eh- I dunno - half a grapefruit, ok, no - with a mint sprig.
You can use more Orgeat if you want - it depends how strong the taste of the syrup is. The idea is to just feel a bit of it. I used Monin brand which is very strong.