To make the render easier on the void, try this.
On Void PSD, find the layer that already has the render boubabi used as an example. Right click on it, and click "create smart object."
Then, double click on the image of that layer, it will open up a new tab, which will be the exact square size that is in the void PSD. Put your render in that file and re size it appropriately. Save that file and go back to the void PSD.
Now your render will be in the void, and it won't be over the square's borders.
Also, here is a simple youtube video that briefly covers some pen tool stuff, and also how to make your shape into a selection like I talked to you about in chat -