First, read this tutorial if you haven't installed the Imagelys Plugin for Affinity Photo.

You can apply Bokeh effects to your images files very easily with Affinity Photo. For Mac and PC only.

With Affinity Photo, in the main menu, click to open and choose an image file.

Then, in the Layer menu, click to Duplicate the Background.

Then, click to Selection Brush Tool and drag the mouse into the flower and make a selection.

 

You can use the Refine Selection tool to improve the selection.

Then, in the main menu, click to Copy and next click to Paste for create a new layer.

Then, hide the Flower layer and hide the Background. Now, click to this layer Background.

First, in the Select menu, click to Grow / Shrink.

Now, drag the trackbar Radius to -28 px and click to Apply button.

Then, click to Cut in the Edit menu.

First, click to Deselect in Select menu.

Next, into the Filters menu, click to Plugins -> Imagelys -> Imagelys Picture Lab.

Now, wait the start of Imagelys Picture Lab application.

First, click to Select one Filter for open the ToolPalette.

Now, click to Effects - Paint Styles 3 and click to Bokeh Effect 07.

Then, in the Filter Parameters dialog box, you can adjust parameters of the Bokeh effect.
Now, click to Apply this filter settings to the image.

After a little while (the rightmost portion of the status bar shows the progress), the rendered effect will be displayed.
Now, you can click the Validate button for validate your work and return to Affinity Photo.

First, show and select the Flower layer. Then, click to Duplicate this layer.

Then, select the Flower layer and select this layer Background.

Now, in the Layer menu, click to Merge Selected.

First, show and select the Flower layer. Then, click to Selection From Layer into the Select menu.

Then, hide the Flower layer. Now, click to this layer Background.

First, in the Select menu, click to Grow / Shrink.

Now, drag the trackbar Radius to 180 px and click to Apply button.

Then, click to Blur -> Depth Of Field Blur into the Filters menu.

First, make an ellipse arond the Flower. Drag the trackbar Radius to 42 px. Then, click the Apply button.

Now, click to Save as in the main menu and enter a filename..

The result of Bokeh effect.
Click on this image to zoom.