Welcome to The Forum . Hard to answer without knowing your experience level. I am looking at the photos you posted. Box joints are OK for making the leg assemblies and I would use a 1/2" straight bit w 1/2" shank, on a Router Table using a jig. You may want to consider some sort of reinforcement under the table to help stop that pesky Wracking hazard. I think even 3" wide hardwood isn't as strong as 3" wide steel leg assemblies. You will also find a lot of helpful ideas and instructions if you search out your questions on YouTube! Hope this helps you to have more fun with woodworking.
"Even bad decisions make good stories"