Clay soil contains minerals and nutrients that plants need, but it is difficult to work with because it is either too wet or too hard when dry. You can opt to build a raised garden on top of the clay soil. If this is not an option, then to make it easier to grow your plants, you must work amendments into the soil to improve drainage.
Start with small sections of the garden bed. Breaking down the work area will make amending the soil less difficult. Dig down and turn the clumps over soil over. Optimal depth is 1 foot; 8 inches is sufficient for most plants. Remove any grass or weed clumps from the clumps of soil. Grass can be composted, but weeds cannot.
Use the rake to break up the clumps. Add one scoop of compost, sand, and bark. Mix thoroughly. Add a scoop of compost and mix again. The soil should begin to soften and feel like bagged potting soil. As you mix the soil, add more compost. If the soil is still clumping, add 1/2 scoop of sand and 1/2 scoop of bark.
Mix together lime, pot ash, and Epsom salt in a ratio of 1: ¼: ¼. This ratio, using the scoop, would be sufficient to cover 100 square feet of garden area. Spread lightly over the garden bed and mix into the soil thoroughly. This will adjust the pH of the soil and add magnesium to it.