If you have the template saved just open it.

Set pptApp = CreateObject("PowerPoint.Application")
pptApp.Visible = True
Set pptPre = pptApp.Presentations.Open(Filename:=Environ("APPDATA") & "\Microsoft\Templates\blank.potx", _
Untitled:=True)
Set pptSld = pptPre.Slides.Add(1, ppLayoutBlank)