Q.How to successfully plant a grisselini hedge ?
I have heavy clay soil dries up in dry weather and water logged in heavy rainy clay soil

Certified GKH Gardening Expert
Our experts say, "The shrub isn’t particular about the soil type as long as it is well-drained. It tolerates a wide range of pH, from acid to alkaline, but you should avoid extremes." So, it sounds like you need to do some soil amendments and pH testing before you plant. Here's an article about how to fix your soil to accommodate your new griselinia hedge: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/how-to-improve-clay-soil.htm
After you get your soil ready and the shrubs planted, here's a helpful article about how to care for your plants. https://www.gardeningknowhow.com/ornamental/shrubs/griselinia/growing-griselinia-shrubs.htm