My false bottoms are usually 2". I silicone the back glass then apply the GS from top to bottom. Remember the GS will shrink once it gets wet and warm. I've noticed it usually shrinks a good 1" on all sides.
Once it's done shrinking (after about a day) I cut the bottom enough to slide the bottom in. Then add the top soil etc...
Once it's done shrinking (after about a day) I cut the bottom enough to slide the bottom in. Then add the top soil etc...