The UK will need to establish the same sort of EEA agreement that grants Norway access to the EU's internal market.
From the 23,000 EU laws currently in force, the Norway EEA has incorporated around 5,000 (in force), meaning that Norway is subject to roughly 21% of EU law. This arrangement facilitates free movement of goods, capital, services and people between the EU and EFTA members.
Free movement of goods means freedom from customs fees, where however food and beverage is excluded (because those are susidised by the EU). Free movement of people means freedom of workers to travel between the non-EU country (Norway or maybe the UK) and EU, however Norway is a part of the Schengen area and the UK is not. Bit of a challenge there for starters.
So, somebody needs to sift through those 23,000 EU laws after June 23rd and pick out the ones we need to adopt, to continue to trade unconstrained with our EU friends.
Volunteers?