Joshua obeyed God, then God showed up!
God never told Joshua HOW he was to cross the Jordan nor HOW to take down Jericho.

Two things preceded God showing Joshua HOW to take down Jericho:
1) Obedience - he circumcised his troops - the opposite thing you would normally do in a war.
Two things to obey:
A- God's general commands - as outlined in scripture.
B- God's specific commands - as He's given to each of us specifically through conviction.
2) Reverence - he removed his sandals, just as Moses did.
Removing the sandals implies that you're staying a while - you're giving your schedule up for theirs. It reveals how important you consider the person to be.
Two Step Process - Obedience brought God's presence to Joshua / Reverence brought God's strategy to Him.
HOLY! In both Moses' and Joshua's case God told them that the "place" they were standing was holy.
The place itself wasn't holy without the presence of God there.
Wherever God's presence is that place is holy - remove your sandals and stay.
This isn't speaking physically, but spiritually.
No building is holy - only people can be holy, and that only through God's presence being inside them.