I've gone ahead and used time-proven dowel joints which are ideal for joining end grain to face grain, regardless of any orientation of panels. James Krenov developed a great technique which I am using to align the dowel holes of the side panels with the top and bottom panels. In the photo above, along with a side and bottom panel there is a small doweling jig also present. This jig is essentially an extension of a side panel with the same width and thickness. I accurately bored holes along the width of this jig and then use the jig to bore holes in the top, bottom panels and side panels. This technique ensures great accuracy and an important note is to secure the dowelling jig to any of the surfaces to have holes bored for dowels. To aid in the alignment, I've inserted two pins on either side of the doweling jig which serve to keep the jig aligned with the surface to have holes bored. With this technique, it is important to keep the reference surface of the jig clearly marked so that the holes are correctly transferred. After all this, I forgot to bore one hole as can be seen in the bottom panel, it was a simple thing to correct though .
Next is to finish plane and hand scrape the individual panels and to then assemble these panels into a carcase, I hope to have this done in the next day or two. Slowly but surely the armoire is coming together.