What was the ark of the covenant physically?
Physically, the ark of the covenant was primarily a rectangular box. It was special because it was overlaid with gold and had a role to play, but in its essential form it was nothing more than a rectangular box, consistent with the Hebrew word for ark meaning a box.
Les teaches that the ark of the covenant, located behind the veil, was primarily a rectangular box. He explains that the Hebrew word for "ark" is the same word translated as "coffin" in the last verse of Genesis, so it simply means a box, not necessarily any certain dimensions. The ark of the covenant was special: it was overlaid with gold and had a role to play, but it was still nothing but a rectangular box. This connects to Moses' ark of bulrushes, which was also a rectangular box daubed or caulked with slime and pitch. The pitch is the same Hebrew word translated as atonement, and atonement is in the blood. Les notes that this little box built for Moses was a place of safety, and God is in all this.