I do not recommend sitting live rock in the sand if you are using a deep sand bed of 4"+. also if you set the rock on top and any animals dig under it. well you get the picture. also the die off will be extrodinary on the sides with direct contact with the sand. Im afraid if you want base rock to be supported off the bottom of the tank that should go in 1st, then sand then live rock on top of the base rock. several others will probably have some suggestions for you. so they will probably weigh in here. set up a list of steps, and follow the steps, be patient and try not to get the cart before the horse. there are alternatives to supporting the reef with base rock. there are reef stands(series of shelves you set the rocks on, plastic pipe supporting live rock just above the sand level, and many others as an example. This is a task you really need to think through and decide where you want to go with your system, how you want it to look, and what versatility you want including the animals you will put in. the system needs to be set up for them to provide as best an environment as one can muster for the animals that will come. good luck. I have rearranged the helpful articles and moved a few of the beginners articles to the top of the article forum. you might find something there that will help you. if you want to follow me, and im not saying my way is the only or best by any means only what works for me with what I want to keep, then put a layer of light diffuser plastic grid down, add sand to top of grid, install base rock such as HIROCK, addwater, and then add live sand and complete the reef with live rock. you will notice my reef is all dry rock. i will seed the reef with 2 or three pieces of premium live rock after the system is up and running. so all my rock is glued together to keep it in place and positioned the way I want it. I hope this helps and dosnt confuse you. There is no right or wrong way to do it except to keep as much water flow around the rock as possible and keep the contact points as small as possible. good luck