The boost theme currently does not support drag / drops of blocks (
MDL-56051), but when using the non-drag / drop method of moving blocks it is unclear where the blocks will actually be placed.
When clicking on the move icon and when selecting the new location, there is no inclination on whether the block will appear BEFORE or AFTER the selected target. (To reproduce simply add 3 blocks to the page in boost and click on the move icon on the third block and try to place it before the first one)
This could easily be fixed by changing the text on the move dialog from "to item" to "after item" (See attached screenshot)