Of course, you can still do all of this manually.
There are several easy to use packages that do it for you, however I recommend the makeicon and makesplash generator to get both icons and splash screens for both iOS and Android.
-
Set
AppIcon
inImages.xcassets
-
Add 9 different size icons:
-
29pt
-
29pt*2
-
29pt*3
-
40pt*2
-
40pt*3
-
57pt
-
57pt*2
-
60pt*2
-
60pt*3.
Accessing Images.xcassets on iOS will look like this:

Putic_launcher.png
to folder[$PrjDir]/android/app/src/main/res/mipmap-*
- 72*72
ic_launcher.png
tomipmap-hdpi
. - 48*48
ic_launcher.png
tomipmap-mdpi
. - 96*96
ic_launcher.png
tomipmap-xhdpi
. - 144*144
ic_launcher.png
tomipmap-xxhdpi
. - 192*192
ic_launcher.png
tomipmap-xxxhdpi
.