Twice bitten, three times shy. After the Slotin incident, prompt critical assemblies by hand were prohibited. Los Alamos then built a series of remotely operated critical assembly machines. There is a fair amount of open source literature on them, especially the "Godiva" series. Some of these machines have experienced criticality excursions that damaged the machine, but spared the biological organisms operating them by remote control.

Which reminds me, I can unfortunately not turn this up, but iirc at one of the national labs they've been working on dismantling a particular set of hot cells and iirc the whole thing has been stalled for a couple years trying to figure out how to do it. Sort of like a "demon hot cell".