You will need some sort of popsicle mold. I used
this 10 pop mold (each pop being about 2½ oz) but you can really do this in whatever you have on hand (little plastic cups or i did a few tests in some go-gurt type of pouches).
The simple syrup can be made well in advance, store in an airtight container up to 2 months in the fridge - just make sure to remove the basil after 24 hours.