Open a new blank drawing in AutoCAD using the metric default template acadiso.dwt.  Switch to a Layout.  Use the Layout Manager to set your plotting parameters such as paper size, etc.  When finished with that start creating your custom title block and border.  Also add in any standard layers, text styles, linetypes, dimension styles, etc. that you would like to have available whenever you start a new drawing.  When completed save the drawing as an AutoCAD Drawing Template (.dwt).  The next time you start a new drawing select your template file as the starting point.  From then on this template will be the default template file whenever you start a new drawing unless you select something different.  Give your template file a unique name such as MyA3Template or whatever.

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