How can I add an Icon to to Box Decoration?

I want to add an Icon to Box Decoration like this you are seeing images on left side.

enter image description here

How do I add this with box decoration

Here is the code:

    Container(
             width: 307,
             decoration: BoxDecoration(
                border: Border.all(color: Colors.blueAccent),
               borderRadius: BorderRadius.circular(10.0),
               shape: BoxShape.rectangle,
             ),
           child: CountryListPick(
            onChanged: (list){
              print(list?.name);
                },
              theme: CountryTheme(
                labelColor: Colors.white,
                isShowFlag:true,
                isShowCode: false,
                isShowTitle:true,
                isDownIcon: true,
                showEnglishName: true,
              ),
            ),
           ),

You can use this widget for a textfield with boxdecoration and icon:

TextFormField(
          key: Key(key),
          controller: controller,
          decoration: InputDecoration(
            prefixIcon: Icon(icon), // <-- left icon
            hintText: hintText,
            border: OutlineInputBorder( //<--- decoration border
              borderRadius: BorderRadius.all(Radius.circular(90.0)),
              borderSide: BorderSide.none,
            ),
            filled: true,
          ),
        )