Satechi just released a new, sleek USB-C dock specifically designed for 24-inch iMacs.
Satechi USB-C Slim Dock: Expand the functionality of your 24-inch iMac
The USB-C Slim Dock for 24-inch iMac is meant to simply plug into your iMac setup and go — no elaborate setup required unless you have a lot of desk space to rearrange. It also has spots to install optional external storage via an NMVe or SATA M.2 solid state drive (SSD). Satechi also claims that the dock's sleek aluminum frame is better at dissipating heat than previous models.
But of course, it is a dock first and foremost, which means it offers a ton of extra ports for all sorts of accessories and hardware expansions. You get one USB-C and one USB-A port, supporting transfer speeds of up to 10Gbps.
It also comes with two USB-A 2.0 ports and a slot for reading micro/SD cards (for digital photos and the like). So between plugging in USB sticks and micro/SD cards and installing your own SSD (tool-less, no less), the new dock can also serve as a beefy storage expansion for your iMac,