During the era of the Second Temple, when the Ark was hidden underground, the High Priest would offer the incense of Yom Kippur in the Holy of Holies without the presence of the Ark, and rest the shovel holding the burning coals and incense upon the foundation stone. 
The Ark of the Covenant
Contents:   Part I,    Part II,    Part III,    Part IV,    Part V,    Part VI,    Part VII