How to run gas tracpipe under patio

I’m a garden designer and the the client wants to run a gas tracpipe from the house to fireplace at end of the garden. I want to be sure that we lay the gas pipe correctly under the patio. Does it have to sit in a bed of sand? Then when running it down the garden, what’s the best place to run it? In planting bed or under lawn? And what is the depth it should be laid in the lawn or planting bed? Does it need any extra piping to be run through? The plumber will be connecting the pipes but the landscaper will be laying it under the patio and in the garden. Thanks in advance.