Learning to make a bolero is a beginner's sewing project. It takes about an hour to make a bolero and the cost is reasonable. The project uses about a yard of fabric and can be done without a pattern, although I recommend using patterns for more difficult styles of boleros.
In this how-to article, I suggest that the reader make a small paper mock-up to understand the shape of the garment and why it can be made with out a formal pattern.
Sketch the shape of the bolero on paper. Cut the paper into the shape. Glue the edges as though they were seams.
Measure your body for width and length of the garment. Add 1 inch on the length for the hem.
Purchase enough fabric to match the length and width requirements. Fold the fabric right sides together as you did the paper model. Leave an extra 1 inch on both sides of the width for ease. Leave an extra 1 inch on the bottom for hem. Using a chalk fabric marker, make the neck curve. Using chalk fabric marker, draw the sleeve and side seam lines. Pin just inside the seam line and cut away excess yardage.
Sew the underarm and side seams. Steam the seams open. Turn the garment right side out. Check the fit.
Finish the raw edges with either seam binding or iron-on interfacing and hem.
See Resources for websites that show how to make this project from a T-shirt
Measure twice; cut once. Remember to add an inch to either side of the under arm and side seams.