Thinking about building another bed

[nnjjohn]

I want to frame out another tomato garden bed in my backyard.. enough room for about a dozen tomato plants.. what dimensions and how deep do I need to tiller up some jersey dirt..would hey work to build a base for leveling a new soil bed in a framed landscape bed of tillered earth? I have enough experience framing and fencing a garden ,, but asking what might work best for building a good bed of soil from the bottom up for a dozen or so plants..My yard in basically jersey soil .. clay red rock sandstone and stones i know i must dig out.. i don't want to go crazy hauling loads of top soil in if i can help it .. was thinking after tilling the lawn to spread broken hey bales and topping it with town earth i can drag in using 5 gallon buckets for a base and from there top it with few bags of potting soil from hd .. for a new garden thanks in advance, John