30-45min depending on how fussy I am about padding the bike with foam.
I use DIY sized boxes.

1. Take out wheels and remove pedals
2. Remove rear D hanger with rear D (wrap it in a paper or plastic bag and secure to chain stays with masking tape)
3. Remove handlebar (some of my bikes are drop bar folding bikes; skip this step if its a flat bar bi-fold bike)
4. Remove seat post.
5. Place in box and pad it out with clothing, some packing material.