Natural Cork is comprised of premium quality, pure grain, natural cork. Its smooth, resilient surface allows pushpins, tacks, or staples to be easily inserted yet still hold firmly. Available in 1/8" and 1/4" and 1/2" by glueing two 1/4" pieces together. For an extra measure of security, flame retardant natural cork is also available.
for Natural Cork Glue Installation instuctions

For Natural Cork Installation instructions

Minimum of 1/4" cork recommended for a bulletin board.  If you use 1/8" cork, it should be glued to a soft backing material.   .