Well... really you can do the regular shipping, depending on the weight of the object plus packaging, and depending where you want to ship to
You can use any box - it doesn't have to be bought at the post office. You can use bubbles wrap (here it costs very little for a large roll) to cushion to avoid any damages.
So, depending on weight and where it is shipped (I use canada post and they have a spot on their site that shows the shipping rate from one postal code to another! Your post office should have it too or you can go in to get a quote in person.
Give the buyer the "10-21 days shipping" or whatever depending where they live, and what shipping is used.