"Star ground" when done incorrectly is a good way to make things worse. You need a good excuse not to have a solid ground plane...
Now, examine your Boost schematic, and trace both current loops. The common part is GND - Input cap - Inductor, and then the current flows into...
- MOSFET ON: MOSFET drain then source - GND
- MOSFET OFF: Diode - Output cap - GND
The correct layout for a Boost has the MOSFET source and the GND pin of the output capacitors right next to each other, and connected to GND plane using the same vias. This ensures than the high di/dt currents created by switching between the two loops described above do not contaminate the GND plane.
This is the most important thing in a DC-DC converter, and violating this rule will turn your ground plane in the vicinity into a minefield of HF spikes.
Also, try to layout these two loops close to each other. This means put the diode next to the FET, so when current switches from one loop to the other, radiated fields are minimized. If the two loops could coincide perfectly, then there would be no radiated field, but this is of course impossible.
For extra goodness, connect the input caps GND pin very close too. The current going through it is smoothed by the inductor, so it is much less of a problem, but there's no reason to go out of your way to find trouble.
Now that your Boost is laid out in a compact form, place the whole group of parts on your board where it needs to be, rotate if needed... and if you need to shove other parts out of the way, do it, but never break the link between MOSFET source and output caps.
Now, you can, if you want, add some star grounding on top... by putting the DC-DC in a corner of the board. Preferably as far as possible from stuff like ADCs and opamps. You can also locate the DCDC on its own ground island, however the cut you just made in the ground plane could turn into a slot antenna.
Adding a very cheap filter like a ferrite bead at the output will ensure the HF currents stay in the local loop, and do not travel through the ground plane to the decoupling caps located further on the output rail. This is not mandatory, but if your design includes sensitive analog parts, it is a plus, even if said Boost does not power these parts. What we're doing here is avoiding injection of high di/dt currents into the ground plane.
Note: for a Buck the nasty loops are at the input, so the focus is on connecting the input cap GND and the lower MOSFET/diode GND at the same point.
Example: using these techniques I have a board with a current shunt and a x20 differential amplifier (AD8210). The output has less than 1LSB noise on my 10 bit ADC, which means <100µV noise on the shunt. It sits squeezed between a H-bridge and two 250 kHz DC-DCs. Double sided board, ground on other side. Layout is the most important part of these things.