I started with 8/4 ash and used a radius template from woodcraft https://www.woodcraft.com/products/mdf-corner-radius-template-4-sided
Then took a jig to get close and finished it with a whiteside flush pattern but in my router and man is that thing a beast!
https://www.amazon.com/dp/B0184W7XP0/ref=cm_sw_r_cp_apa_glc_fabc_FXHJB99VCYBBZE56FM2W