This is going to sound very very dump but I'm not getting the logic of creating a custom record with a Sublist... what I need is: Custom Record, Inside this Custom record a Sublist with columns, So I would be able to

record.create

then

record.setSublistValue

which will allow me to create one Record and hold 20 sublist lines with information related to that record only using 2 governance units, when I try to create a sublist within a custom record is asking me for a search and I don't get the logic of that, I just want to be able to define an empty sublist with columns that belongs to that custom record... the same way I define fields within that record...