You have a good example in that wall hanging. Be sure to measure the panel in several places to see if you need to do any squaring. Measure and cut the borders before you put them on. If your first top border is 26 3/4, make sure the bottom one is the same. Your sides will be 34 + the width of the first borders after that first seam.
Usually a narrow border in a strong color and a wide border in a coordinating fabric looks good without adding too much work, though you can go with just one.
Measure, measure, measure and sew an exact 1/4 inch seam and you'll be fine.