well it is not so easy, but it is do-able. i've done this without a tiller. we just dug up as much of the big chunks of clay that we could. then add bags of compost, shredded leaves, humus. i never add topsoil. shredded pine bark works too. some of this you can get by the truckload. some communities give compost. if you use bags of humus like from lowe's or home depot, use at least 20x15 which is 300 of them! it is best to build raised beds if at all possible. with flower beds you only need maybe 6-12 inches for the roots. i mulch everything afterwards. i made a bed in spring and it was quite difficult. but just a few months later (now) in fall, it is much easier to dig and plant there. throw as much organic matter as you can in there, like coffee grounds, mowed (shredded) leaves, grass clippings, and even vegetable wastes and eggshells.