Abstract: A flow base system (1) for subsea wells is disclosed, the flow base system comprising a header pipe (2) for production fluid extended through the flow base system, wherein from opposite sides of the header pipe (3) a set of flow base modules (2), respectively, is connected for supply of production fluid to the header pipe (3) via individual branch pipes (10) connecting the header pipe (3) with a Christmas tree (XT) interface (11) arranged for vertical connection to an XT respectively. The flow base system (1) is installed in a well template structure (18), wherein a flow base module (2) respectively is inserted into each well slot (S1-S4) formed in the well template structure (18).