you can just place the leather between two rocks it will attach in a few days
so far your tank looks great , take your time a reef isn't built in a day
this can show you what you can achieve
than I added this one
than I combined both tanks to my my current tank
it takes time and lots of dedication and patients as things grow out ,
ask lots of questions and you'll get there, this tank is coming up on three years now.
like everything I started small than grew as all the coral and fish grew and all coral and fish moved with it . lots of work no doubt but the reward priceless