Since these are wrong, undo the action (CTRL-Z) and start again, remembering to select the object. This time, if we divide 1585 by 12 we will get 11 slices, using a value of 132. The process will go to completion now, so there are a few more options to include. This time, change the layer option to create a new one:
I am leaving the slice thickness at the default, since I am only cutting the slot with scissors. If you are using a laser cutter or a CraftRobo, you would want to calculate the slot thickness and adjust appropriately.
When you click OK, give the layer a name:
And when you click OK here, the measure dialog shows we now have 11 slices:
Click OK and the base of the screen shows the calculation progressing. When it is finished you are asked if you want the Original Selection to stay hidden. Say Yes and the parameters for the next set of slices (X) comes up with the same spacing:
Again, make a new layer, and continue and name the layer and get the measure dialog box for the X slices.
Now you can continue to make the flattened slices and set the gap between them.