It is recommended to use our AD7768 Evaluation Board | Analog Devices design example as a reference for a good layout.
There is also DN477 - Driving Lessons for a Low Noise, Low Distortion, 16-Bit, 1Msps SAR ADC and Design Guidelines for High-Performance, Multichannel, Simultaneous-Sampling ADCs in Data-Acquisition Systems (DAS) | Analog Devices describing design techniques to achieve the desired ADC performance.