Making a beam isn't rocket science but a little thought and patience will go a long ways towards ending up with a serviceable product.
Type of wood is not critical but a durable hardwood species such as Ash, Oak or Maple will resists nicks a cuts a bit better.
Shape..The pictured beam is 1.5 X 6 X 60. From the nose to where it is full width is 12".The photo with the knife shows the proper curvature you want to achieve.
Tools..If you really have some time on your hands you could do it with a pocket knife.Shape the nose with a saw,your choice.My choice of non powered tools for shaping the curvature would be a draw knife.If you have one and know how to use it.It will be a 2 hour project total.A hand plane will work but is much slower.Use sandpaper with a sanding block to finish it.60 grit paper is as fine as you want to use.Sand diagonally across the grain.Sand with the grain and you will be there for ever.You only need to shape about 3 feet of the beam.
Take your time and do it right.A well made beam will last you a long time.