By doing without a cable adjuster you're doing it the hard way. It's possible, so in the lowest ring position with the chain on the largest sprocket at rear and the cable slack, adjust the "L" screw so that the chain just misses the inside plate on the FD cage. Now take up the slack on the cable so that it is just taut and no more. Now try the change.
If however this is a Road triple we are talking about then a cable-adjuster will be needed to get the fine adjustment necessary for this to work properly.