Standard form is another topic that I find requires lots of practice to ensure students are confident with the key ideas and skills needed to succeed. With this in mind I want to have plenty of tasks that provide opportunity for practice without repetition. I want there to be a point to the practice and the easiest way to do this is to set them a challenge that requires the use of the skill I'd like them to be practicing. Here is a small example of what I might use.
I've set the students 2 challenges here. Some students, through better understanding, will have an idea with what they want to begin with. Students struggling to get started are told to put the numbers in randomly and perform the addition. All students are then encouraged to look at their answers and perhaps try switching 2 of the boxes in the addition and seeing how it impacts their answer.
You might well want to replace the 4 given numbers so that they include negatives too. Personally - I want students adding standard form by manipulating one of the numbers so that they both have the same 'counting unit' (power of ten). Once this is done we can use the distributive properties to add the numbers together.
For this to work well the powers have to be close enough to make it an efficient use of their time hence me choosing 4 consecutive numbers.
For a downloadable version of the task follow the link: https://drive.google.com/file/d/1l9ZC3SnzNfg3O0sgmn84nCHr4k3-GLhL/view?usp=sharing