Research Dumping Grounds

1. (optional)Attach the front to the back If your tunic is cut with a separate front and back, flat-fell them together at the shoulders. It doesn't matter which way the seam goes. Sew this flat-felled seam completly.

The nice thing about having a shoulder seam is that it's easier to fold the tunic.. and it's easier to tell the front from the back (front neck line dips down further). That said, shoulder seams are entirely optional.
2.Attach the arms to the body. Place the arm and the shoulder wrong sides together with the arm on top. Sew the first line of stitches for the flat-felled seam. Start and stop the stitches about 1-2 inches from the corner of the arm. See picture, below-left, for visual.
3. Attach the gussets to the arm and the body of the garment and 4. Finish the bottom of the arms If you do it right all of the seams will fold together beautifully. It just needs to be done in the right order.

a. Line up gusset with corner of arm and flat-fell completely.
b. Sew gusset to body, only sew half the flat-fell seam.
c. Line up gusset with other corner of arm. Sew first seam of gusset and then continue on and sew the first seam along the bottom of the arm. Finish flat-felling that seam (gusset and arm)
d. Sew last side of gusset to body. Only sew half the flat-fell seam.
e. Finish the flat-fell seam around the gusset and the shoulder.

5. Attach the gores to the bottom of the garment (I prefer to start at the top of the gore and work towards the hem). Attach the bias edge of the gore to the straight edge of the garment.
6. Flat fell the seam between the two gores. I prefer to work from the top of the gore towards the hem.

That's it. Just hem the bottom, the wrists and the neck line and you have it.