The motherboard design of the ASRock H61M/U3S3 is not anything too unique but is certainly sufficient for this black micro ATX motherboard.
The Intel H61 chipset only supports two DDR3 DIMM slots, so as such that's all the memory options for this motherboard. On each side of the memory slots are the 24-pin and 8-pin power connectors. For anyone still actually running a reputable old 20-pin + 4-pin power supply, this motherboard can still function.
There are six SATA ports on this motherboard, two of which are Serial ATA 3.0. Covering the H61 chipset is a small aluminum heatsink that is passively cooled. Below the chipset are two USB headers and the front panel headers.
This micro ATX motherboard has only one PCI Express 2.0 slot, two PCI slots, and one PCI Express x1 slot.
The area around the LGA-1155 CPU socket area is free of any obstructions that would cause problems for some after-market heatsinks.
The I/O panel ports on this motherboard include two PS/2, one VGA, one DVI, one HDMI, four USB 2.0, two USB 3.0, one Gigabit Ethernet, and three analog audio jacks.