After bowling you must not stand in or walk/run up the land, obstructing the view of your opponent. When you come off the mat, you should step to the side or back.
walking across the land
It is common to see people walk across the green to the head after their second wood has been bowled. This can interfere with other games and means bowlers may have to pause before delivering their wood.
Doing this can cause the bowler to lose their land. Doing this to your teammates is counter-productive!
Please be considerate and walk around the green. Thanks.
References From The Laws Of The Game
6.4. A player must not attempt to affect the running of any bowl, nor follow it up in such a manner as to obstruct the view of the opponent.