There are lots of options these days to rent a nice workstation by the hour or even by the minute and it would be great if people could share their experience with various options.
We have had good luck with AWS app streaming which can be set up through the web console and offers a wide range of options from small machines through huge GPU workstations running windows or linux. Realistically it takes a while to figure out how to get it running but once you do it’s easy. I’ve also got a project to make bootable cloud disk images running Slicer but this is even more complicated to use.
There are many providers and convenience, cost, and network latency may make one or another option better. Search for terms like “vdi” (virtual desktop interface) and “virtualization” to see options. You just need any kind of desktop with a browser that lets you install the slicer application. If you are only doing segmentation a GPU could even be optional.