How to get SP.ClientContext to work on basic aspx.page?

Question

I am trying to get JSOM to work on a basic aspx page created in Sharepoint Designer. But I have been unable to get SP.ClientContext to work, it is undefined and I get the error: "Sys.InvalidOperationException: Cannot find current web URL information on the page." I have tried using both executeFunc and and SP.SOD.executeOrDelayUntilScriptLoaded with no success. And typing _spPageContextInfo into the console returns undefined so I'm thinking that I need to add something else to my webpage. I added all the js calls included in an ootb SharePoint page so that shouldn't be in issue either.