Begin by placing 3 sides of your box as illustrated below. Each of the panels should be grouped.

Before you start you should do a "save as" and call the file box (or whatever your box is called)-iso.ai

Select the top panel

Option-click with the scale tool on the point of origin. Type 86.6 in the verticle field.

The top panel should squish down like this.

Using the sheering tool, Option-click on the point of origin again. Enter 30 degrees.

The box should look like this.

The last step for the top panel is to use the rotate tool. Option click on the point of origin and enter -30 (that is minus 30) It should look like this.

Next use the black arrow (selection tool) to select the front panel. Remember, it should be grouped.

Use the sheer tool. Click on the point of origin and type in -30. It should sheer the front panel like this.

Now use the rotate tool. Option click on the point of origin and type in -30.

Click on the last panel with the selection arrow.

Click on the point of origin using the sheer tool. Type in 30 degrees.

Click on the point of origin using the rotate tool and type in 30.