if you can build hoplites
(ANY SORT levy or classical)
use them as auxilary (kyrene and sicilia can produce them with L3 regionals)
spread them 6 deep and they're unmovable by a phalanx until they start pushing as in attacking outright but still would survive long enough for your legionaires to flank them.

Quite simple

4-5 phalanx hoplites or some sort with light infantry or somethign behind them (2 stretched cohorts would work) with 8-10 deep legion cohorts all stacked on the flanks and horsemen behind the hoplites
after 10 or so mintues (all units in defense mode) the phalanx would be exhausted or tired and order ur flanking legionares to flank them by 1 going outwards and 1 charging then the flanking one could aim torwards the center.
Once the center turns to attack your legionaires, order hoplites/ auxiliaries to attack
after a min or so (half would prolly route by now) calvalry charge and instant route...
easy :D ive done it A LOT!!!! well itll prolly grind your legionaires odwn somewhat but make sure every time designate 2 or 3 cities for recruitment near the front lines and 1 or 2 back at italy...