Here's one way (there are loads of others):
* Make sure "Snap to objects" is turned on (on the standard button bar)
* Make sure "Scale line widths" is turned off (on the selector tool infobar)
* Draw a box
* In the Selector tool, Drag it and when it snaps into position alongside the outline of the original, click the right mouse button to drop a copy

You can either drop all the copies you need one by one, snapped next to each other, or:
* Drop, say, just 3 copies to start with
* Select the first box and the 3 copies (4 in all)
* Drag those until they snap into position alongside the original 4 and right-click to drop copies of all 4
* Then select all 8 and repeat, etc.

This very quickly creates lots of boxes with few clicks.

If you are creating a 2 dimensional grid, then select a whole row, drag that to snap into place below the original position and right-click to drop a copy, etc, etc...

Phil